Veterans of D-Day gathered at the Imperial War Museum on Tuesday morning to mark the start of the series of commemorations during this week.
The Duke of Gloucester and Dambusters actor Richard Todd joined 100 veterans for the ceremony, which was also attended by Field Marshal Montgomery's son.
The Imperial War Museum's Christopher Dowling said: "It is the most significant gathering of D-Day veterans in the UK. Some cannot go to the beaches so this is the next best thing.
"It is quite a historic reunion. We have worked closely with the Normandy Veterans Association and we are hoping it will be a day to remember."
The ceremony began with a performance by Portsmouth's Royal Marines Band.