William and Kate's first journey as husband and wife will be escorted by nine of the coolest heads the Metropolitan Police has to offer - the force's famous grey horses.
But while the matter of invites has long been settled for human guests at the wedding, the animals of the Met's Grey Escort are still waiting to learn if they will have the honour of accompanying the royal couple's carriage.
Guests must worry about what to wear - the horses of the Grey Escort are also assessed on whether their coat will match their peers.
A lone mounted inspector will ride in a position known as the 'pointer' ahead of a sergeant and three constables.
Animals, which have to be grey in colour, are used as operational police horses and work on general patrols and cover events such as football matches.
On the big day the horses and officers will not purely be used in a ceremonial capacity, but they will also assist in the event of an incident.
A selection process has identified the best 11 greys for the job. They have demonstrated a calm temperament and are now in the process of being put through various exercises and routines.
The extra two horses have been selected to ensure there is sufficient cover.
The Mounted Branch has led processions for many years including Princess Diana's wedding, the Duke of York's wedding, the funeral of the Queen Mother, Trooping the Colour and some state visits.