There is an old Hotel/Pub in Marble Arch, London which used to have gallows just down the same road that Marble Arch was on. Prisoners were taken
to the gallows (after a fair trial of course) to be hung. The horse drawn wagon, carting the prisoner was accompanied by an armed guard, who would stop outside the pub and ask the prisoner if he would like "ONE LAST DRINK."
If he said YES it was referred to as ONE FOR THE ROAD. If he declined, that prisoner was referred to as ON THE WAGON. So there you go...!!! Just one more good reason to never go "ON THE WAGON."
