An east London police horse, the longest-serving grey in the Met force, will form part of the mounted escort for newly-weds Prince William and Kate Middleton once they tie the knot on Friday.

Annabel, who is based at Bow Stables and has been with the police since 1997, will play a crucial role on the historic day by forming part of the nine horses making up the “Grey Escorts”.

As part of the Met’s Mounted Police branch, the 21-year-old horse will escort the royal procession from Westminster Abbey to Buckingham Palace following Friday’s wedding ceremony.

Annabel has previously been involved in the state opening of Parliament, the Trooping of the Colour and the state visit of Mexican and Canadian officials.

All the horses are chosen to ensure they have the “temperament to cope with the event” according to the police and practice events took place in Hyde Park.

The escort will be led by a mounted inspector, known as the “pointer” who will lead the procession including the married couple and other members of the Royal Family.

Behind the “pointer” there will be one mounted sergeant and three constables to make up the front of the escort and the same number of officers and horses at the rear.

The officers will wear a uniform of a silver lanyard and silver striped breeches.

The Mounted Branch also led the procession for the wedding of William’s parents, Prince Charles and Princess Diana, the funeral of his great-grandmother, the Queen Mother and the wedding of the Duke of York.