The attack had been carried out by a lone German bomber flying behind a squadron of Allied planes as they returned to the UK.
The Nazi bomber dropped two 50kg high-explosive bombs on Collingwood. One fell into the playing fields but the other hit the accommodation block, killing 33 young men and wounding 38 others.
A spokeswoman for the Royal Navy said: ‘They were all volunteers, signed up to serve king and country, and most were just 17 or 18 years old. Often, this would have been their first time away from home, having been in the Royal Navy for just over a fortnight.’
But victims' families were initially told the trainees died in an ammunition accident.
Ken Waugh, archivist at the HMS Collingwood Association, said the event was hushed up by the navy.
It was feared that if the truth was known, it could have been used as propaganda for Hitler’s Nazi war machine.
Ken, who attended the Fareham naval establishment in 1955, said: ‘As far as I can remember it was kept fairly quiet. Nobody knew about it when I was at Collingwood.
‘I didn’t know about this until I joined the Collingwood association years later.’
It wasn’t until years later that the navy revealed how the men died.
Now, each year, a service of remembrance is staged at Collingwood, with the latest taking place on Saturday.
Civilian and military personnel on the base held a minute’s silence at the spot of the tragedy
Reverend Jonathan Backhouse, one of Collingwood’s chaplains, spoke of the loss of the young sailors and the tragedies of war, both then and in the present day.
The Establishment’s Base Warrant Officer, WO1 Martin Watson read out the names of the young trainees who died before the Last Post was played by a bugler from Her Majesty’s Royal Marines Band, Collingwood.
Commanding Officer, Captain Catherine Jordan, then laid a wreath.
Today a tree stands on the site of the accommodation hut, as a permanent reminder of the tragedy and, ahead of the service, 33 memory cards were tied to its branches, each one displaying a poppy, a copy of the sailor’s prayer and the young trainee’s name and service number.
Speaking after the service, Captain Jordan said: ‘We will always remember those who lost their lives here during the war. Tragically, they never lived to fulfil their potential and undertake the service for which they had volunteered, but we will never forget their sacrifice.’
Ken added he was delighted the memory of the men was remembered by the next generation of sailors and said: ‘It’s good that we still remember them.’HMS Collingwood is home to thousands of sailors and is the Royal Navy's largest training establishment. It is the headquarters of the maritime warfare school.