Thanks for the kind words peeps. I should never listen to a suggestion from paddy irish again... [joke].
I set off at 17:45 and felt really great for the first 8 hours. I was making great progress and passing riders from all around the globe. It was a warm evening and I only put on warm clothing around 2-3am. My knee was twinging a little which I put down to the cold, as it does in winter, but when I arrived at Fougeres (and after 2 puntures in the space of 500m), I was feeling a little tired and could feel a twinge in my left knee when pressing down on the pedal. I sorted out the issue of repeat punctures, incorrectly set brakes rubbing against the tyre, and presseed on at the back of a groups of mixed riders. I was ok, hanging on the back and cruising along at ~28kph but needed a wee and pulled off the road. When I attempted to make up time, my knee was really complaining. As I started each uphill in the rolling landscape approaching Tintineac, my knee was in a lot of discomfort. I was ~20km away and had time to consider what was wrong. I came to the conclusion that the fall on the exit from the Pentlands must have re-aggravated my old cruciate ligament injury. I decided that rather than continue on and risk more damage, I'd just abandon. I have completed this ride - 4 years ago, and was in a good enough shape to complete again, if not for this injury re-surfacing.
My journey back to Paris was not without slight hiccup. The ticket for Rennes could only be sold for a train which had not set off yet, as it was an e-ticket, and the controller's (conductor) scanner would not accept the ticket, but she let me on anyway. Then at Rennes, I had to ask a platform staff member where the cycle carriage would be. Then the TGV controller initially after asking me if I had a booking and if I had a bike bag, said no. But an English speaking platform assistant intervened and translated that I had not intended on travelling and that due to my injury, I was returning to Paris via train, as I had no other option. At this point the controller said yes and I was onboard. he TGV is super! Non stop from Rennes to Paris at speeds of over 300kph. Certainly puts our old stock into the shade.
Anyway I made the most of my DNF and visited Versailles and Paris, as well as having meals with cycling friends who were not riding PBP, but there for a holiday.