The Duke and Duchess of Cambridge are to join the Queen on her royal barge during the River Thames pageant celebrating the Diamond Jubilee.
William and Kate will be at the Queen's side as she receives the well wishes of up to a million spectators expected to line the river banks and open spaces.
The spectacular water-borne extravaganza featuring a flotilla of 1,000 ships, boats, yachts and other vessels will be one of the highlights of the extended Diamond Jubilee weekend in June. Organisers hope to recreate scenes not seen on the river for more than 300 years, since the reign of Charles II.
With the Queen and Duke of Edinburgh on the lavishly decorated royal barge will also be the Prince of Wales, the pageant's patron, the Duchess of Cornwall and Prince Harry.
On the prow of the royal barge, a luxury cruiser called the Spirit of Chartwell, will be an ornate gilded sculpture featuring Old Father Thames, a pair of scaly sharp-toothed classical dolphins - a symbol of the Thames - and the royal cipher at the centre.
A lavish red velvet banner decorated with a version of the royal coat-of-arms made from more than half a million gold-coloured buttons will hang from the stern.
Other members of the Royal Family will travel on neighbouring vessels in the royal squadron towards the front of the flotilla.
Chelsea pensioners will make up a Guard of Honour for the Queen and Philip and Charles and Camilla at Chelsea Pier when the royal party begin their day on the river on Sunday June 3.
Havengore, the vessel that carried Sir Winston Churchill's coffin during his state funeral in 1965, will be used during the pageant by the Duke of York and his daughters Princess Beatrice and Princess Eugenie, the Earl and Countess of Wessex, the Duke and Duchess of Gloucester and Prince and Princess Michael of Kent.
The Princess Royal and her husband Vice Admiral Sir Timothy Laurence will travel on the Trinity House No 1 Boat while the Duke of Kent and Princess Alexandra will be aboard the RNLI Diamond Jubilee.