The bomb release button from the Lancaster Bomber which destroyed the Mohne Dam during the famous Dambusters raid has fetched just under £40,000 at auction in Northamptonshire.
The RAF relic - described as one of most important items from the Second World War - released the successful "bouncing bomb" that crippled the Nazi war effort.
The Bakelite switch was pressed by bomb aimer John Fort aboard the Lancaster Bomber of 617 Squadron and was the fifth aircraft to attack the dam on May 17 1943.
The heroic crew had flown from RAF Scampton in Lincolnshire, before breaching the heavily fortified dam and flooding the western Ruhr region in the Eder valley.
The mission - called Operation Chastise - changed the course of the war and was later immortalised in the 1955 classic film The Dambusters.
The pilot, David Maltby, gave the button - measuring 50mm x 28mm - and other items from the plane to the school where his father was headmaster.
Hydneye House in Hastings, East Sussex, then dedicated a small museum for the items before it closed in the 1960s.
But the vendor, a close family friend of the pilot, decided to sell on the memorabilia and the button itself went for £39,500.
Also on sale were four large marbles used by bomb inventor Barnes Wallis in the development of his weapon, which sold for £18,500.
The items from one of Britain's most memorable war victories were sold publicly for the first time by JP Humbert Auctioneers in Whittlebury, on July 1.
Auctioneer Jonathan Humbert said: "These are incredibly rare and very historic items of a simply unrepeatable nature.
"We anticipated global interest in these evocative and iconic pieces of 20th century British history and I am pleased to report that interest exceeded expectation!
"This button quite literally changed the course of world history by causing catastrophic flooding of the Ruhr Valley thus almost certainly shortening the war.
"There were a whole series of bombs that were dropped and this is the button that arguably saved millions of lives.
"In any event- it helped convince people that the Allies were winning- and that is often how wars are won or lost.
"The button hasn't had a long life but my word it has had an eventful one."