Can't see this verse here or elsewhere quoted - originally from Diz Disley, if I remember right.

"Newlyweds while in the carriage
Should not consummate their marriage
While the train is standing here at Crewe
To perform this natural function
Kindly wait 'til Clapham Junction
Where you'll find there's sod-all else to do!"

Come to think about it, it might have been Derek Craft of 1812, rather than Diz.

Alan