John Barkman's from the USA, although an AUK member. So Gethin Butler is the fastest Brit. There's an interesting connection with Sir Hubert Opperman. Both Gethin and Sir Hubert have held the LEJOG record, and rode PBP in very similar times, although Butler was on his own largely, having missed the first start in 2003.
I've been doing some research around the LEJOG, and a significant figure in the early days was G.P. Mills, who won Bordeaux-Paris in 1891, and the paced LEJOG record in the same year. Mills worked as chief engineer for Humber who made bicycles, motorbikes and cars.
One of the pacers for Mills on Bordeaux-Paris was Charles Terront, who won the first PBP on a Humber bicycle.