Paris Brest Paris (PBP) LFGSS 2011

indeed some of them ride incredibly fast considered the distance and lack of sleep (I presume they don't do 'kips'). I just read that the fast lot in the 2007 PBP had an average of about 30kph: 44 hrs 50 mins... wow.

the PBP pdf brochure is here

In 2003 at 24 hour point as we rode in to Loudeac, the group of fast riders who had set off two hours ahead of us were on their way back on the opposite side of the road, amazing how they can keep that speed up for that amount of time.
A Belgian won it with a time around 45 hours and I think they had two hours penalty for rule bending.