IF one Allied leader came out of the Second World War covered in glory it has to be Winston Churchill. Stalin was discredited by the communist brutalities of the 1930s and 1940s; Roosevelt came into the war late and died before it was over; De Gaulle was tainted by the collapse of France in 1940; Harry Truman has never been forgiven for vaporising Hiroshima and Nagasaki; the

Chinese supremo Chiang Kai Shek proved to be one of Asia's more

dismal warlords. Only Winston Churchill saw the war through from start to finish with his reputation unblemished. His familiar bulldog scowl remains one of Britain's most powerful and enduring icons.

But every icon has its darker side. Churchill is no exception. A collection of once-secret documents buried in the Public Record Office (PRO) in London conjure up a very different Winston Churchill. They reveal a war leader with an enthusiasm for the poison gases of the First World War who was prepared to defy international protocols and spray them on any German force which set foot on Britain. And who, long after the threat of invasion was over, pressed his service chiefs for plans to ''drench'' (his word) the civilian populations of 100 German cities with phosgene and mustard gas.

Churchill's readiness (eagerness even) to use gas as a weapon is one of the Second World War's better-kept secrets. In his own account of the war he mentions it only briefly, and in a series of footnotes. But from the very beginning of his premiership - and particularly after the debacle of Dunkirk - Churchill was determined that Britain should have huge stocks of poison gas, the weapons needed to deliver it, and

the will to use it first. It was a grim strategy which plainly appalled many of Britain's military chiefs.

Poison gas was first used in earnest on the Ypres salient on April 22, 1915, when the German army unleashed 170 of tons of gaseous chlorine on French, Algerian and Canadian troops. The Allies were outraged by this perfidy. Kitchener accused the Germans of stooping to tactics which vie with those of the Dervishes' - and promptly got the British War Cabinet's permission to go on a gas offensive.

And so began a deadly (and escalating) tit-for-tat. Chlorine was replaced by phosgene which was replaced (in 1917) by mustard gas. Along hundreds of miles of the Western Front thousands of tons were of gaseous chemicals were loosed into the prevailing winds. By the end of the war thousands of men on both sides had choked to death, or been blinded, or scarred with blisters or had their lungs seared.

The numbers were bad enough. But it was the nature of the injuries (blindness, scarred faces, liver damage, ruined lungs) and the sheer randomness of gas warfare that appalled the world. An unpredictable wind could easily send clouds of poison in among non-combatant women and children, something that seemed unthinkable during the First World War. It was to prevent such a calamity that 140 nations - including all the major powers - signed up to the Geneva Protocol of 1925 prohibiting . . . ''the use in war of asphyxiating, poisonous and other gases, and of all analogous liquids, materials and devices.'' And particularly, the first use of such weapons.

But having agreed not to use gas weapons the major powers went on developing them. Britain was no exception. All through the 1920s and 1930s the scientists at Porton (now Porton Down) developed ever more lethal cocktails of gas. The Porton scientists were particularly interested in delivering poison gas from aircraft either by bombs or, better still, spray tanks. And it was the Porton scientists - in a long paper dated 1930 and entitled The Casualty Producing Power of Mustard Gas When Sprayed Directly On To Personnel - who produced the classic definition of a gas casualty. It was: ''A person who is burned to a degree which will prevent him, however willing, from performing any military duty, no matter how pressing the military situation may be.''

In September 1939 that military situation became pressing indeed when Britain and France declared war on Hitler's Germany. One of the War Cabinet's first acts - in October 1939 - was to step up the production of phosgene and mustard gas. And while His Majesty's Government had promised at Geneva in 1925 never to initiate the use of poison gas, by early 1940 people were having second thoughts. A meeting of the Joint General Staff and the Air Staff in April 1940 warned that ''our present Government policy is that we should use gas only in retaliation, but it is possible that, when the gloves are really off, and the war has become really grim, there might be a change of heart.''

That ''change of heart'' was not long in coming. A few months later the war became ''really grim'' when the remnants of the British Army had to be plucked off the beaches of Dunkirk and shipped back across the channel to lick its wounds.

Invasion by the all-conquering Nazis seemed a real possibility. On June 15, only two days after the evacuation from Dunkirk was complete, the Chief of the Imperial General Staff Sir John Dill produced what has been described as ''one of the most explosive memoranda of the war''. It is entitled The Use of Gas in Home Defence.

The time had come, Dill told Britain's military chiefs, to abandon the Geneva Protocol of 1925 and to use poison gas whether or not it was deployed by the Germans. Particularly if they invaded the coast of Britain. ''Enemy forces, crowded on the beaches, with the confusion inevitable on first landing would present a splendid target,'' Dill wrote. ''Gas spray by aircraft under such conditions would be likely to have a more widespread and wholesale effect than high explosives. It can, moreover, be applied very rapidly, and so is particularly suitable in an operation where we may get very little warning.''

The ends, Dill concluded, justified the brutal means. ''At a time when our National existence is at stake, when we are threatened by an implacable enemy who himself recognises no rules save those

of expediency, we should not hesitate to adopt whatever means appear to offer the best chance of success.''

Dill's memorandum raised a firestorm of opposition. The Director of Home Defence wrote back that: ''We should be throwing away the incalculable moral advantage of keeping our pledges and for a minor tactical surprise; and the ultimate effects of retaliation by the enemy would be very serious in this overcrowded little island.'' And Dill's own chief of staff, Major General Henderson, was appalled at the idea that Britain should initiate the use of gas. He replied scathingly to his boss: ''Some of us would begin to wonder whether it really mattered which side won.''

At which point Prime Minister Winston Churchill entered the fray - on Dill's side. It may be that Dill had been whispering in Churchill's ear. In a memo to his close military adviser General Hastings ''Pug'' Ismay (dated June 30) Churchill pitched his formidable weight behind the poison gas warriors. ''What is our gas output per month?'' he demanded to know. ''It should certainly be speeded up. Let me have proposals. Supposing lodgements (ie enemy bridgeheads) were effected on our coast there could be no better points for application of mustard than these beaches and lodgements.''

Churchill agreed with General Dill that Britain should not wait around for the Germans to use the gas first. ''In my view there would be no need to wait for the enemy to adopt such methods'' he wrote. ''He will certainly adopt them if he thinks it will pay. Home defence should be consulted as to whether the prompt drenching of lodgements would not be a great help. Everything should be brought to the highest pitch of readiness.''

It was an instruction that could not ignored. Britain's gas-making and gas-delivery machine swung into top gear. Chemical plants at Randle and Rocksavage in Cheshire began working flat out to produce mustard gas, phosgene (and some tear gas). A third factory was opened at Springfield in Lancashire.

As the war ground on a total of 5300 men and women - 4300 industrial workers, 600 researchers and chemists and 400 service personnel - were at work producing Britain's stocks of poison gas. Another 500 people from the Minister of Aircraft Production were employed making mobile containers and spray tanks for the aircraft which would ''drench'' the beaches of eastern Britain with gas if the Germans ever set foot on them. Four types of aircraft were earmarked for the job; Lysanders, which would carry two 250lb spray tanks; Battles and Blenheims equipped with two 500lb tanks; and Wellington bombers kitted out with a brace of 1000lb tanks. Twelve gas-attack squadrons were assembled, two of them in Scotland; at Lossiemouth on the Moray Firth and Grangemouth on the Firth of Forth. The rest were scattered down the east coast of England as far south as West Malling in Kent. (The Lysander squadron

at Grangemouth was later transferred to Macmerry in East Lothian.)

This prodigious gas apparatus is a tribute to Winston Churchill's ability to cajole, bully and persuade. He never stopped fretting about the need (as he saw it) to have large stocks of poison gas ready and waiting for delivery. A string of memos in the PRO testify to Churchill's preoccupation (obsession, almost) with gas. In July 1940 Churchill was pressing to have ''preparations complete''. In October 1940 he wanted to know why the plant at Randle was not working flat-out. When told there were difficulties he urged: ''Press on. We must have a great store as they will certainly use it against us when they feel the pinch.''

Churchill's relentless pressure paid off. All through the war British factories continued to churn out gas weapons. And in dazzling variety; mustard bombs, phosgene bombs, mustard airburst bombs, mustard spray bombs, mustard 25lb shells, mustard howitzer shells, mustard mortar shells, phosgene mortar shells, chemical mines, bulk contamination vehicles. By 1944 Britain's chemical arsenal was huge. The RAF was supplied with more than 700,000 poison gas bombs and spray tanks; the British Army had almost 4,500,000 shells and mines stuffed with poison gases. It was more than enough to encounter anything the Germans might throw at Britain.

By May 1941 it was clear that the British were prepared to use poison gas anywhere on the British archipelago - including neutral Eire. ''The use of gas in Ireland (including Eire) would be ordered and controlled by the General Officer commanding British troops in Ireland '' one top-secret memorandum declares. In other words, if the Germans had tried to use Eire as a back door into Britain the RAF would have sprayed the beaches of Ireland with mustard gas and/or phosgene.

But even more startling is Churchill's readiness to use gas towards the end of the war, when the threat of invasion was over. By July 1944 the Germans were reeling. The Allied armies had broken out from Normandy and were fighting their way across northern France. Rome had fallen and British and American divisions were pushing up through Italy. German cities were being pounded day and night by British and American bombers. On the

Eastern Front the Red Army was poised to crash into the Reich. In short, the Axis powers were being ground down into ruin.

All of which makes Churchill's plan to use gas against German civilians all the more startling. It may be that he was panicked by the German V-1 rockets which were then falling on and around London. He was certainly worried that the Allied landings at Normandy might become boxed in. Perhaps he saw a way of coercing the Germans into an early surrender. But whatever the reason, his lengthy ''personal minute'' of July 6, 1944, to General Ismay is Winston Churchill at his most chilling.

''I want you to think very seriously over this question of poison gas,'' he told Ismay It is absurd to consider morality on this topic when everybody used it in the last war without a word of complaint from the moralists or the Church. On the other hand, in the last war the bombing of open cities was regarded as forbidden. Now everybody does it as a matter of course. It is simply a question of fashion, changing as she does between long and short skirts for women.''

Churchill saw a distinct strategic advantage in deploying the gas. ''I want a cold-blooded calculation made as to how it would pay us to use poison gas, by which I mean principally mustard. We will want to gain more ground in Normandy so as not to be cooped up in a small area. We could probably deliver 20 tons to their one and for the sake of the one they would bring their bomber aircraft into the area against our superiority, thus paying a heavy toll.''

Churchill goes on: ''If the bombardment of London really became a serious nuisance and great rockets with far-reaching and devastating effect fell on many centres of Government and labour, I should be prepared to do anything that would hit the enemy in a murderous place. I may certainly have to ask you to support me in using poison gas. We could drench the cities of the Ruhr and many other cities in which a way that most of the population would be requiring constant medical attention. We could stop all work at the flying bomb starting points. I do not see why we should always have all the disadvantages of being the gentleman while they have all the advantages of being the cad ''

Churchill wanted the gas to be used ruthlessly. He instructed his military chiefs that when the time came '' to drench Germany with poison gas let us do it 100%. In the meanwhile, I want the matter studied in cold blood, by sensible people and not by that particular set of psalm-singing uniformed defeatists which one runs across now here now there.''

The Prime Minister ended

his four-page minute with a Churchillian flourish. ''Pray address yourself to this,'' he told Ismay. ''It is a big thing and can only be discarded for a big reason. I shall have to square Uncle Joe and the President (ie Stalin and Roosevelt) but you need not bring this into your calculations at the present time. Just try to find out what it is like on its merits.'' At first, Churchill's minute met with a stunned silence. The Imperial General Staff (and Ismay) probably thought that they had disposed of the Prime Minister's ''first use'' of gas plans back in 1940. Now they saw that they had not. And by July 25 Churchill was growing impatient. He sent a curt note to the faithful Ismay saying: ''I now request this report within three days.''

Three days later, Ismay duly submitted his report. It included a list of every German city with a population of more than 100,000 people. Among the cities targeted for ''drenching'' with mustard gas and/or phosgene were Berlin, Cologne, Dusseldorf, Essen, Frankfurt, Bremen, Hamburg, Dresden, Leipzig, Stuttgart and 50 others. A few days later Viscount Cherwell (the German-born scientist Frederick Lindemann) weighed in with the calculation that the RAF had enough mustard gas available to contaminate ''some 900 square miles - more than the areas of Berlin, Hamburg, Cologne, Essen, Frankfurt and Cassel put together.

But while Britain had the means it did not have the will. Churchill (and Lindemann) were more or less alone in their enthusiasm for ''drenching'' the cities of Germany with poison gas. The military saw it as a strategy that could hinder the Allied advance across Europe - as well as bringing down the condemnation of the world. ''On balance,'' Ismay told Churchill, ''we do not believe that for us to start chemical and biological warfare would have a decisive effect on the result or the duration of the war against Germany.''

At which point Churchill backed off, grumbling. He did, however, send Ismay and the Chiefs of Staff a sour little memo on July 29. ''I am not at all convinced by this negative report'' he wrote. ''But clearly I cannot make head against the parsons and the warriors at the same time. The matter should be kept under review and brought up again when things get worse.''

In the event, things did not get worse The Axis continued to crumble. Nor did Adolf Hitler, even in his darkest hours of defeat, sanction the use of chemicals and give Churchill a reason to deploy his stocks of poison gas. By May 1945 Hitler was dead and the war in Europe was over. If Britain came out of the war with its reputation intact it is due to the good sense of the generals - and not to Winston Churchill. If the military had acted on Churchill's personal minute of July 6, 1944, and ''drenched'' every city in Germany with poison gas, Britain may well have emerged from the SecondWorld War as one of the 20th

century's criminal states.

I WANT you to think very seriously over this question of poison gas. I would not use it unless it could be shown either that (a) it was life or death for us, or (b) that it would shorten the war by a year.

It is absurd to consider morality on this topic when everybody used it in the last war without a word of complaint from the moralists or the Church. On the other hand, in the last war the bombing of open cities was regarded as forbidden. Now everybody does it as a matter of course. It is simply a question of fashion changing as she does between long and short skirts for women.

I want a cold-blooded calculation made as to how it would pay us to use poison gas, by which I mean principally mustard. We will want to gain more ground in Normandy so as not to be cooped up in a small area. We could probably deliver 20 tons to their one and for the sake of the one they would bring their bomber aircraft into the area against our superiority, thus paying a heavy toll.

Why have the Germans not used it? Not certainly out of moral scruples or affection for us. They have not used it because it does not pay them. The greatest temptation ever offered to them was the beaches of Normandy. This they could have drenched with gas greatly to the hindrance of our troops. That they thought about it is certain and that they prepared against our use of gas is

also certain. But the only reason they have not used

it against us is that they

fear the retaliation. What

is to their detriment is to our advantage.

Although one sees how unpleasant it is to receive poison gas attacks, from which nearly everyone recovers, it is useless to protest that an equal amount of HE will not inflict greater cruelties and sufferings on troops or civilians. One really must not be bound within silly conventions of the mind whether they be those that ruled in the last war or those in reverse which rule in this.

If the bombardment of London really became a serious nuisance and great rockets with far-reaching and devastating effect fell on many centres of Government and labour, I should be prepared to do anything that would hit the enemy in a murderous place. I may certainly have to ask you to support me in using poison gas. We could drench the cities of the Ruhr and many other cities in Germany in such a way that most of the population would be requiring constant medical attention. I do not see why we would always have all the disadvantages of being the gentleman while they have all the advantages of being the cad. There are times when this may be so but not now.

I quite agree it may be several weeks or even months before I shall ask you to drench Germany with poison gas, and if we do it, let us do it 100%. In the meanwhile, I want the matter studied in cold blood by sensible people and not by that particular set of psalm-singing uniformed defeatists which one runs across now here now there. Pray address yourself to this. It is a big thing and can only be discarded for a big reason. I shall of course have to square Uncle Joe and the President; but you need not bring this into your calculations at the present time. Just try to find out what it is like on its merits.

The full text of Churchill's letter