Wouldn’t it be great if this were not a joke: the security contingency that was in place in the event that Kate Middleton tried to run away just before the wedding.

After protracted, top-secret negotiations between royal staff from Clarence House and representatives from the Metropolitan Police, MI5 and elements of the military, a compromise was agreed. In the event of Operation Pumpkin being put into effect Ms Middleton will be permitted to run out of Westminster Abbey with her bodyguards trailing discreetly at a distance. Plain-clothes undercover police, MI5 officers and SAS soldiers stationed in the crowd will form a mobile flying wedge ahead of her, clearing a path for the fugitive future princess to escape down.

Prince William will then have a limited time, the subject of tense negotiations between Clarence House and security chiefs, in which the path behind Ms Middleton will be kept open for him to go after her, after which the mobile protective cordon will close again at the Abbey end due to lack of manpower and the Prince will have let his bride slip through his fingers.

If Wills reacts fast enough, however, he will be able to chase after his fleeing fiancee for just under half a mile.