Guests including Sir David Attenborough and Sir Tom Stoppard expected at Order of Merit lunch at Windsor Castle today

A luncheon for Members of the Order of Merit is being given by the Queen at Windsor Castle today.

The Order is a special honour awarded to individuals for great achievement in the fields of the arts, learning, literature and science.

Members expected to attend today's lunch include the Duke of Edinburgh, broadcaster Sir David Attenborough, playwright Sir Tom Stoppard, British military historian Professor Sir Michael Howard, World Wide Web inventor Sir Tim Berners-Lee and politician the Right Honourable Baroness Betty Boothroyd.

Other Members of the Order who are not expected to attend today include the Prince of Wales and the artist David Hockney.

There can be a maximum of 24 Members - there are currently 23 - as well as additional foreign recipients, which in the past have included Nelson Mandela and Mother Theresa.

The Order was created by King Edward VII in 1902.

Past British holders have included Florence Nightingale, Sir Winston Churchill and the founder of the Scout movement General Baden-Powell.