Crowds strained for a view of Her Majesty, who wore a pale primrose suit and floral hat, as she rode in an open carriage from Buckingham Palace to Horse Guards Parade. Armed police, and officers in bullet-proof vests were on patrol in case of a terrorist attack but the loyal crowd enjoyed a great day.
Flag-waving fans surrounded the Queen Victoria memorial in front of the Palace and cheered the royal party.
The Queen Mum, who will be 97 next month, got a special cheer as the Duke of Edinburgh helped her take a place at the front of the balcony.
After a fly past a booming voice called for "Three cheers for Her Majesty" and the enthusiastic crowd responded - to the Queen's delight.