It will be the first time that many of them have met in the 60 years since the outbreak of the conflict.

Up to 2,000 will attend the service at Westminster Abbey

In just three days from 1 September 1939, up to 1.5m children in British towns and cities were exiled from their homes in efforts to protect them from German bomb attacks.

Tens of thousands had a marvellous time, but many were ill-treated by their hosts and some died in exile.

The BBC's Clarence Mitchell meets evacuees

Friday's memorial event has been organised by the newly-formed Evacuees' Reunion Association.

The former evacuees will march from HorseGuards Parade to a memorial service at nearby Westminster Abbey, which will be attended by the Duke and Duchess of Gloucester.

Many enjoyed evacuation, others were ill-treated, and some died

During the service a book of remembrance, containing the known names of all those who died as evacuees, will be placed on the high altar.

The book will include the names of 77 children who drowned when the City of Benares, the ship carrying them from Liverpool to Canada, was torpedoed.

RAF fly-past

Immediately after the service a wreath in memory of the children will be placed by the Duke and Duchess on a memorial stone.

Actors and former evacuees Jack Rosenthal and Maureen Lipman

This will then be taken by the Royal Navy to be dropped in the Atlantic in the area where the ship was sunk.

The RAF is also expected to pay tribute to the evacuees with a fly-past following the service.

There will also be a special presentation at the Imperial War Museum in London, of poems written by men and women serving in the armed forces at the time of the outbreak of the war and the evacuation.