A relic of aviation history goes on public display this week, 60 years to the day after it dropped out of the skies over the Firth of Forth.

The starboard wing fuel tank is all that is believed to have survived from the Junkers 88 dive bomber which became the first German aircraft to be shot down in the Second World War and the first dispatched by a Spitfire.

Remarkably, it lay buried on an East Lothian beach for more than 50 years until finally unearthed, thanks to the efforts of two aviation historians and a bit of luck.

Two auxiliary fighter squadrons were scrambled to engage the 12-strong German force on October 16, 1939. From Turnhouse came 603 (City of Edinburgh) and, from Drem, the newly-delivered Spitfires of 602 (City of Glasgow).

Dogfights raged just over the rooftops of Portobello and the attack exposed a weakness in Edinburgh's defences in their first real test - the air raid sirens failed to go off.

Two Junkers 88s were shot down. The first was deliberately ditched near a fishing boat off Gullane by Oberleutnant Sigmund Storp to help save his crew. He and two others survived and were rescued.

The second aircraft crashed off Crail 15 minutes after being attacked by 602 Squadron. Its pilot, Hauptmann Helmut Pohle, the mission commander, was the sole survivor.

Among the crowds who watched was a young boy, Bob Brydon, now 67. ''I saw it all from Portobello promenade. They were flying so low they rattled roof tiles,'' he said.

Mr Brydon also witnessed recovery of wreckage through his aunt's boyfriend, a bomb disposal officer.

''There was a piece of the starboard wing which they buried on the beach. I made a careful note of where it was buried,'' he said.

There it lay undisturbed for 50 years although the subject did come up in conversation with his colleague, Mr Willie Henderson.

''I had been looking for it for years but I realised we were talking about two different locations. It was just a chance that I thought I might be looking in the wrong place,'' Mr Henderson said.

Four years ago, on a walk with his family, he noticed a piece of metal sticking out of the undergrowth and sand. Further research in Germany confirmed it was from a Junkers 88.

''We can't be 100% certain if it came from Storp's aircraft, rather than Pohle's, but it is highly likely,'' he said.

Mr Brydon is not divulging the exact location but the section will be put on display along with photographs, archives, and other material at the Museum of Flight in East Fortune, East Lothian, next Saturday. A Spitfire is also due to fly past to mark the 60th anniversary.

The wreckage may also have greater historical importance since no trace has been found of other parts which were recovered at the time.

''This came as a surprise to me but I don't think the raid has really received the attention it deserves,'' Mr Brydon said.

At the time, it had enormous propaganda value. Pathe News reconstructed Storp's crash several days later, giving rise to the myth that it happened off Port Seton, rather than further down the coast.

Both German pilots had flown with the Luftwaffe in Spain and may have taken part in the bombing of Guernica in 1937.

Mr Brydon said Storp appeared to have planned the Forth raid to show that capital ships could be attacked and sunk by aircraft, a tactic demonstrated with devastating effect by the Japanese at Pearl Harbour two years later.

Contrary to another myth, the Forth bridge was not the target. Hitler had given specific orders to avoid any civilian casualties. For this reason, other ships in the dockyard were left untouched.

Although not reported at the time, the raid was also partially successful. Two ships, HMS Edinburgh and HMS Southampton suffered damage and 16 crew members on HMS Mohawk were killed.

This was also a time when chivalry still had a place among aviators - 602 was originally styled the City of Glasgow (Gentlemen's) Bomber Squadron.

Surviving letters point to the mutual respect and comradeship between Storp and Pohle, who is still alive at the age of 92, and RAF pilots who once had them in their sights. Storp gave his Luftwaffe gold ring to the fisherman who saved his life and became a friend of the family. Total war was to come later.

The question of which Junkers was shot down first has been the subject of a long-running dispute - with claims made by both 603 (Edinburgh) and 602 (Glasgow).

Mr Brydon and Mr Henderson are convinced that 603 has the better claim. Nor can they be accused of bias - both are members of 602 squadron's museum association.

''It is probably 603 which got Storp's plane. But we haven't told them that,'' said Mr Brydon.