Britain on Wednesday paid tribute to those who took part in D-Day, promising to "always remember" the sacrifices made by the Allied soldiers who invaded France by sea and air to drive out the forces of Nazi Germany in the World War II operation.

With guests waving British flags, appearances from veterans, recollections and readings - and some tears in Queen Camilla's eyes - the British ceremony took place in Portsmouth, the main departure point for the 5,000 ships that headed to Normandy on June 6, 1944.

"Today we come together to honour those nearly 160,000 British, Commonwealth and Allied troops who, on 5th June 1944, assembled here and along these shores to embark on the mission which would strike that blow for freedom and be recorded as the greatest amphibious operation in history," King Charles said.

"So, as we give thanks for all those who gave so much to win the victory, whose fruits we still enjoy to this day, let us, once again, commit ourselves always to remember, cherish and honour those who served that day and to live up to the freedom they died for."

About 4,400 Allied troops died on D-Day. (Reuters)