The Queen and Duke of Edinburgh will attend a service to mark the 100th anniversary of the Order of the British Empire.
Almost two thousand holders of the Order's awards, from Knights and Dames to those who have received a CBE, OBE or MBE, will attend the service at St Paul's cathedral.
The congregation will be formed by people from all parts of the UK and Commonwealth, and will include a number of honorary award holders.
King George V established the Order in 1917 to reward outstanding contributions to the First World War effort and today it recognises the work of people from all walks of life.
The Queen is the sovereign of the Order of the British Empire and the Duke of Edinburgh is its Grand Master.
A service for the Order is usually held every four years at the cathedral, the last service being in 2012, with the Queen attending every eight years.