The Queen has arrived at Westminster Hall for a lavish Diamond Jubilee lunch to be greeted by a fanfare of trumpets.
Some 700 guests are attending the event - being funded by the Livery companies of trades and professions ranging from the historic Mercers and Grocers to International Bankers.
Representatives of charities and the armed forces are among those dining with the royal family and the National Children's Orchestra of Great Britain is providing a musical accompaniment.
The Prince of Wales, the Duchess of Cornwall, the Duke and Duchess of Cambridge and Prince Harry are also attending the meal.
William has been placed at the Engineers and Arbitrators table, while Kate will be joined by the Master Glovers and Pattenmakers. Harry is on the Fruiterers and Gardeners table.
The Duke of Edinburgh's place has not been taken by another member of the Royal Family.
Guests will dine on marinated Uist Island salmon with Lyme Bay crab, followed by saddle of Welsh Cambrian Mountain lamb with braised shoulder of lamb, grilled Isle of Wight asparagus, Jersey Royal potatoes and an aptly named Jubilee sauce. The "symphony of dessert" is chocolate delice, bread and butter pudding and berry compote with Sandringham apple sauce.
A Ceylon tea will also be served made from a bush planted by the Duke of Edinburgh during a state visit to Sri Lanka in 1954 on the Pedro Tea Plantation in Nuwara Eliya.
Master Mercer Thomas Sheldon praised the Queen's "unstinting" devotion to duty. "Much has changed in the last six decades. But it has been the age of Elizabeth," he told the guests. "You embody the very best of our national values. You are our constant in a changing world."
Mr Sheldon added: " We are particularly sorry that the Duke of Edinburgh is unwell and cannot be with us but we all wish him a speedy recovery."