THE GUILT-STRICKEN confession of an ex-Luftwaffe pilot, the schoolboy memories of an Irish-born British army officer and a pile of 50-year-old intelligence files have conspired to re-open the great mystery of Irish neutrality in the Second World War: why did Germany bomb the "open" city of Dublin on the night of 31 May 1941?

The attack on the North Strand in Dublin killed 34 Irish civilians and wounded 90, prompting apologies from Nazi Germany and claims by the British that de Valera's neutral Ireland was at last paying the price for "sitting on the fence" during the war against the Third Reich. After the war, Germany paid compensation to the Irish Republic for what it described as a military error, while British intelligence officers suggested that the German aircraft - en route to a target in the United Kingdom - had been deliberately steered towards Dublin by RAF experts who had "bent" the Luftwaffe direction-finding radio beams.

Now an elderly German - living in Canada and calling himself only Heinrich, but insisting he was one of the Luftwaffe pathfinder pilots on the night of the Dublin bombing - has broadcast an appeal for forgiveness over RTE, Irish state radio. He was asked to bomb Belfast, he said, but his two squadrons of 30 aircraft approached Dublin by mistake. "Please forgive me for this mistake which was beyond our control," Heinrich told reporter Micheal Holmes. "There was no wrongdoing on our side. Everybody was upset, not only the members of the [German] air force, but politically as well."

Download the new Independent Premium app Sharing the full story, not just the headlines

Heinrich, however, muddied the moral waters by expressing admiration for Hitler - "I thought him quite a guy," he said. "I was impressed because he let me criticise my boss [Air Minister] Goering. I thought he was a very kind man. I say he was a weakling because he was too kind." And Heinrich did not express any sorrow for the people of Belfast, supposedly the real target that night, who endured two terrible nights of Luftwaffe raids the previous month in which almost 1,000 Protestant and Catholic civilians were slaughtered by hundreds of Luftwaffe bombers.

Enter, then, Colonel Edward Flynn, second cousin of neutral Ireland's Minister for Coordination of Defensive Measures, one-time British army officer and former special adviser to the Bahraini government. "I was home in Ireland from my boarding school in England and I remember hearing a broadcast by William Joyce [Lord Haw Haw] in which he warned that Amiens Street railway station in Dublin might be bombed," he said. According to Colonel Flynn, Joyce took exception to the large number of Belfast bombing refugees arriving by the hundred at Amiens Street. The station, now called Connolly after one of the the executed leaders of the 1916 rising, was only a few hundred yards from North Strand, where the German bombs exploded.

"I also remember Joyce complaining that the Irish were shipping cattle to Britain from the docks at Dundalk and threatened that it would be bombed if this continued," Colonel Flynn said. "And my father and I were in Dundalk the night a German aircraft bombed the quayside there a few days later. It was a clear night and we actually saw the plane coming in from the north." Dundalk, a tiny port on the Irish east coast, was indeed shipping cattle to Britain during the war.

A contemporary issue of the Irish Independent reported, under heavy censorship, that the aircraft's origins were "unknown", but a spokesman for the Irish army's Archives in Dublin explained last week that intelligence files compiled after the attack on George's Quay, Dundalk, in the early hours of 4 July 1941, noted that the aircraft had approached from the north (as Flynn described it) and that a bomb fragment bore "the imprint of the German eagle".

Histories of the Luftwaffe's Blitz on Britain later suggested that in their efforts to deflect the bombers, British scientists had "bent" the German radio direction beams - the Knickebein or "crooked leg" system of navigation - and sent German aircraft in the direction of neutral Ireland. In fact, the British could not "bend" the beams, which were sent out from occupied France and Norway. But they could interfere with the radio signals and force aircraft to lose their way.

An intriguing series of reports from the once secret intelligence files of the Irish army suggest that this had already happened on 28 May 1941 - two days before the Dublin bombing - when large numbers of aircraft, almost certainly German, flew up the Irish coast and then became confused when they reached the Irish capital. Many of them were then heard to drop their bombs over the sea after presumably realising they were not over a UK target.

Irish neutrality has thrown up many myths. Churchill, outraged that the Irish Prime Minister Eamon de Valera refused to loan Britain three former Royal Navy ports which the pre-war British government had handed back to Ireland, believed that de Valera was secretly allowing U-boats to refuel in west of Ireland ports and their crews to come ashore - a claim later proved to be false. The British were obsessed that the German legation in Dublin would radio prior information about the D-Day landings to Germany, even though Irish army intelligence had already removed the Germans' radio set. Almost every German spy parachuted into Ireland was captured at once.

But the bombing of Dublin remains one of the great mysteries. Did Berlin wish to punish de Valera for sending his fire brigades north to help Belfast after the April bombings in Northern Ireland? Did Germany wish to warn Ireland against sympathising too greatly with Belfast victims of the Blitz? Or were the Germans angry at Ireland's trade with Britain?

Oddly, a German broadcast three weeks before the Dublin bombings warned that "to gain their ends, the British intend to bomb Eire and then declare that this crime was carried out by Germany". But the bomb fragments, Germany's apology and now Heinrich's admission make it clear that the Luftwaffe was to blame. Had the bombers been misled by the British? Quite probably, although they would not have been able to redirect the planes. But given Churchill's state of suppressed fury with de Valera, the British would probably not have been upset if they had sent the Luftwaffe off to bomb Dublin.

t Robert Fisk is the author of "In Time of War", a study of Irish neutrality in the Second World War.