While the rest of the capital was sleeping, hundreds of soldiers rode on horseback through the streets of London to rehearse the State Procession for the Queen's Diamond Jubilee.
Members of The Household Cavalry Mounted Regiment rode at dawn from the Palace of Westminster along Whitehall to Trafalgar Square, then through Admiralty Arch and along the Mall to Buckingham Palace.
The route was lined with personnel from the Royal Navy and Royal Marines, Foot Guards and Massed Bands of the Household Division, the Princess of Wales's Royal Regiment and the Queen's Colour Squadron of the Royal Air Force. In total, some 2,000 servicemen and women took part in the rehearsal.
Thousands of flag-waving well-wishers are expected to turn out for Tuesday's spectacle.
An investigation has been launched into how unpaid workers bussed into London for the Diamond Jubilee celebrations were left stranded.
The Archbishop of Canterbury Rowan Williams spoke of the Queen's lifelong dedication to her people, her country and the commonwealth.
The Queen has a packed schedule on the final - and climactic - day of the Diamond Jubilee weekend.