Southwark cadets were out in force representing the Sea Cadet Corps at the annual flag raising ceremony, now in its sixth year, which was attended by Chelsea Pensioners, Yeoman Warders and other veterans.
Mayor of London Boris Johnson said: "This year, the nation commemorates the centenary of World War I and we remember the men and women who served in, lived through, or lost their lives during that terrible conflict.
"One hundred years on, the UK Armed Forces continue to defend the UK and its interests, not only by promoting peace in countries such as Afghanistan, but also by providing security, delivering aid, tackling drug smugglers and fighting terrorism across the world.
"And so, today, our thoughts embrace all those in active service in areas of unrest, those who lead them, guide them and care for them abroad and at home and, of course, we remember those we have lost."