The construction of a Second World War US base in St David’s was crucial to protect the island’s interests as well as those of the Allies, a Canadian historian has said.

Duncan McDowall, speaking to the Commission of Inquiry on historical loss of land on Friday, said the 1940 baselands deal was thought to be beneficial to the US, the UK and Bermuda.

Dr McDowall said: “It was a strategic advantage for the Allies to have a base in the Atlantic and, conversely, if the Germans got it, it would put America in a Pearl Harbour-situation.

“The U-boats were cutting off supplies and there was a real risk that if Britain collapsed Bermuda – a British colony – would be in jeopardy.”

Dr McDowall said that the bombing of Britain was a motivation in the decision to proceed with the deal, it was far from the only factor.

He said: “Defeating Nazism is an endeavour that I think all Bermudians had to recognise.

“White Bermudians who tended to see themselves as British – after all it was a colony – automatically came to Britain’s defence.

“England was in peril and if England fell, we would be next, and we were a vulnerable little island in the Atlantic.”

Dr McDowall said that, although America did not enter the war until after the bombing of Pearl Harbor in 1941, the country had already started to help the UK in secret.

He said: “We know that Churchill and Roosevelt established a sub rosa relationship that was preparing America for entry into the war and that had a military technological hinge to it.

“The German submarines were already ravaging transatlantic convoys and Britain was militarily beleaguered, so the Americans were beginning to feed military aid into it.”

Dr McDowall said base deal allowed Britain to get 50 American destroyers and, while the ships were “very old-fashioned”, they were absorbed into the Royal Navy.

He highlighted that the Bermuda base was listed as a “gift”, but it was a part of the lend-lease deal.

Dr McDowall said that the Battle of Britain – the RAF’s fight for air supremacy over the UK against the German Luftwaffe – had ended in victory for Britain before St David’s was identified as the location of the proposed base, but the tide of the war had not yet turned.

He said added that the base was also seen as having value for Bermudians.

Dr McDowall said: “There was a local advantage to this as the U-boats were preying on the supply ships that were coming into Bermuda. American tourism by 1940 had pretty much stopped because people didn’t want to be at sea.

“There was a closer-to-home element in this of ensuring that Bermuda could protect itself and that meant the station being able to be placed there to protect the convoys and protect the colony.

“What was needed was a real airport base that could control the Atlantic but also provide a way station for aircraft being ferried to Europe. A land base was pretty important.”

He highlighted the sinking of the SS Birmingham, which was torpedoed on the way to Bermuda, as an example of the direct threat to Bermuda.

Dr McDowall said: “Bermuda is a small place. If a ship doesn’t come, you start to run out of things pretty quickly.”

He said a base in Bermuda offered America a good way to protect convoys and America’s borders.

Dr McDowall said: “It was geographically very handy and that was one of the distinct roles of Bermuda after the American Revolution.

“For Britain it was a kind of offshore post to keep an eye on the Americans and now the roles were reversed as the Americans thought it would be in their interest to have a presence in Bermuda to defend their shores.”

He said that the US at first proposed a base in Warwick, but a Bermudian committee pushed the project to St David’s.

He said: “That initial location, cutting across Warwick, the Bermuda committee did a good job of fending that off because it would have completely bifurcated the colony and cut into a vital section of the economy.”

Dr McDowall confirmed that the potential impact on tourism was probably one of the factors that were considered in the move away from Warwick.