It's rumoured that the great Freddie Phillips created the extra Pugh for musical reasons. Otherwise, as the driver of the engine perhaps it was thought Barney McGrew had greater importance - or maybe it was a stipulation in his contract?

Whatever the case, in the World of the Human Arts there are few things e'er so perfect as Pugh, Pugh, Barney McGrew, Cuthbert, Dibble, Grub. Don't go asking it to bits.