AN ALLEGED and probably apocryphal radio exchange dating from the Gulf war sums up the operational credo of the Special Air Service, Britain's elite band of shadow warriors.

An eight-man patrol lying in the desert deep inside Iraq reputedly signalled back to its headquarters in Saudi Arabia: ``Surrounded all sides by four enemy divisions.'' To which the reply flashed back: ``Good. You are obviously in the right place.''

David Stirling, the regiment's founder, believed success in waging war lay not in mastering the art of the possible, but in being able to achieve the impossible. That goal remains the key to SAS triumphs and the foundation of its fearsome, though often over-hyped, reputation.

SAS troopers have been variously labelled as supermen or cowboys. Irish Republican lawyer Paddy McGrory once described them as ``an unholy priesthood of violence''. Public perception of their role and capabilities probably lies somewhere in between.

Successive governments have revelled in the Regiment's mystique (serving and former members always refer to it as the Regiment and seldom ``the Sass'') and encouraged the Army's veil of silence over its activities worldwide. Successive Prime Ministers have also fallen under its spell, seeing it as the ultimate instrument of clandestine state sanction.

Before the 1980 storming of the Iranian Embassy at Princes Gate in London, the SAS was a largely unknown quantity. Only a handful knew or cared that it had been fighting a savage little five-year war in Oman from 1970 onwards, a war that cost it 13 unsung dead.

But as nuclear weapons rendered the prospect of all-out conflict between the superpowers unthinkable, and armies numbering millions of men faced each other in impotent stand-offs from the Arctic to the Mediterranean, the Cold War glowed brightly at the edges.

Denied the outlet of full military confrontation, both power blocs jostled for influence and strategic advantage in brush-fire clashes elsewhere. The SAS became Britain's shock troops in that 40-year succession of skirmishes around the globe. Oman, Malaya, and Aden were the new proxy battlefields in a war where the bullets and the casualties were all too real.

There is a clock at Bradbury Lines, the SAS headquarters compound in Hereford, which bears the names of those killed in action or in operational accidents since 1950. It currently lists more than 100 fatalities. Those who survive their tours of duty with the Regiment call it ``beating the clock''.

Separating myth from reality has, until recently, been next to impossible. SAS operations were secret. Its officers and men maintained a close-mouthed camaraderie which naturally bred rumour and speculation among the uninitiated. It was the basic building block of legend. The few incidents which came to public attention served only to enhance and exaggerate the ``Super-trooper'' image.

To some extent it was a policy which paid dividends. When Harold Wilson, the master manipulator of the media, announced in 1976 that he was sending the SAS to Northern Ireland, it sent ripples of fear through the Provisional IRA's military set-up and ripples of laughter through those in the know.

The psychological impact of the announcement, and of later SAS ambush operations in the province, was out of all proportion to the numbers deployed.

The Regiment had been involved, in secret, since 1972, when a handful of officers and experienced NCOs were attached to line battalions to teach them the rudiments of counterterrorist warfare and the value of patient and unobserved intelligence gathering.

When Wilson dropped his bombshell there were only 11 SAS troopers available from the unit's four ``sabre'' squadrons. They had just returned from Oman and were fit, suntanned, and experienced in fighting tribal insurgents in the deserts and harsh mountain jebels on the rim of Arabia's Empty Quarter. They were to find the backstreets of Belfast and the blackthorn-hedged wilderness of South Armagh a new but equally deadly kind of desert.

From a total strength of 400 men, no more than a single SAS squadron, about 70 to 80 men, was ever deployed to the province. Most of the time only a couple of dozen officers and troopers occupied the upper floor at Bessbrook Mill, the nerve-centre for anti-terrorist operations along the border.

Though the SAS played significant roles in the Falklands and Gulf wars, the Irish connection has consistently placed the greatest strain on the character and image of the unit.

Its troopers were accused of ``shoot-to-kill'' tactics in Ulster, the hit-squad elimination of key IRA activists, and forays into the Irish Republic in illegal snatch operations. The killing of three unarmed IRA members in Gibraltar in March, 1988, in front of civilian witnesses was hailed as proof-positive of the Regiment's role as government assassins.

The satirical magazine, Private Eye, published a cartoon at the time in which one trooper asks another: ``Why did you shoot him 16 times?'' The second soldier replies: ``Because I ran out of bullets.''

In the 25 years of The Long War in Ulster, the SAS killed 35 IRA members. During the same period it arrested and brought to trial more than 100. Given its intelligence resources and firepower, it could have wiped out the 300 to 400 ``known players'' available to the Provos in a matter of weeks if there had been any deliberate policy.

The three terrorists cut down in a hail of bullets in Gibraltar were, as admitted by the IRA's Army Council, an active service unit on a reconnaissance mission for a bombing outrage. They were challenged and then shot when they reached for what the troopers involved took to be weapons.

No chances could be taken. The street was busy with innocent civilians. The SAS team simply took out what was perceived to be an immediate threat. In a close-quarters fight, instant reaction spells the difference between living and dying. Death, the SAS believes, is nature's way of telling you that you have been in a gunbattle and lost.

The chosen few - perhaps one candidate in 10 - who manage to surmount the immense physical and psychological process of unit selection emerge, indisputably, as trained killers. They are not, however, assassins. Beyond the realms of movie make-believe and uninformed liberal claptrap, there is no such thing as shooting to wound.

SAS troopers who want to survive are taught to lay down rapid, accurate fire that is designed to drop an adversary instantly. This involves aiming for the head and chest. Anything less opens the possibility of retaliation. Survival against terrorists or trained enemy soldiers demands ruthlessness.

They are simply good soldiers, the best of the best that Britain can offer. Until recently they also maintained a solid tradition of sensible and life-saving democracy, paying only a passing regard to the conventions of rank. It was known as ``wigwam parliament''. On operations, the advice of the most experienced member of a team, not necessarily the most senior, often dictated the ensuing course of action.

The Regiment was seen as more of a meritocracy, run principally by NCOs, than as a rigid, formal unit in which the officers led and the men followed like sheep. Officers qualifying for service seldom do more than one or two three-year tours of duty before returning to the mainstream ``green machine'' Army structure and readier promotion prospects. NCOs and troopers frequently serve for 10 or 12 years and find it impossible to revert to a spit-and-polish regime.

For many, there is no life beyond the SAS, only a restless downslope. When you have gone the extra yard, and lived on the edge, nothing else will ever duplicate that adrenalin high.

The Regiment is a synthesis of all that can be achieved with a focused assembly of men who are willing to endure, think for themselves, carry out lonely missions far beyond immediate help - often deep behind enemy lines - and still maintain a sense of humour. And all that, in the majority of cases, without public recognition of their achievements.

A spate of books written by veterans covering SAS operations in the Gulf, Ireland, and South America has, however, created something of a crisis of identity. It has also generated a crackdown by the Army's senior hierarchy and the secrecy-obsessed Defence Ministry. Further revelations have been forbidden, and the perceived despoilers of mythology have been cold-shouldered by the Regimental association and barred from entry to the Valhalla of Bradbury Lines.

The powers-that-be appear to believe the SAS legend can be sustained only by a blanket ban on disclosure of operations that have gone wrong. To them, the Regiment exists to make good failures of Government policy, and must be above weakness or defeat. There is also, to some degree, an element of jealousy abroad in the ``green machine'' about SAS autonomy and lack of accountability to the regular chain of command.

The SAS, like any organisation, is far from perfect. It failed in its strategic objective during the Falklands War. It was meant to strike directly at air bases in mainland Argentina and destroy the Super Etendard aircraft and their deadly cargos of air-launched Exocet missiles which posed the most potent threat to the British task force. The plan was scrapped after a single, abortive reconnaissance.

It failed to supply the celebrated Bravo Two Zero patrol in the Iraqi desert with functioning communications equipment or even a realistic briefing on terrain and likely enemy threats. The result was four unnecessary deaths. It was war and it happens.

It lost 19 experienced and irreplaceable men in an accidental helicopter crash in the freezing South Atlantic during a routine cross-decking of men from one ship to another in 1982. It was the single biggest toll in the modern history of UK special forces.

Despite the devastating blow the Regiment carried on in the spirit of its core philosophy. A single verse, inscibed on the headquarters clock-cum-memorial, epitomises the essence of the SAS.

It reads simply:

We are the pilgrims, master,

We shall always go a little further,

It may be beyond the last blue mountain,

Barred with snow,

Across that angry or glimmering sea.

IAN BRUCE