Well attempted this last weekend and failed, suffered a cut tyre wall after Seathwaite, ended up walking back to the Newfield in and having a couple of pints before biviing just behind the pub near the bridleway.
From the 51 miles I did I can certainly say that there is some tough riding, but I am familiar with much of the route from Black Sail Pass onwards and I'm not unconvinced that a strong and determined rider couldn't do it in one hit. I plan to have another crack at in September, aiming for sub 40 hours, still not brave enough not to take a bivi!
The biggest mistakes I made were that I took the wrong bridleway on two occasions (had a v basic gps and was map reading) then had to double back to make sure I covered everything and got credited for my time. If you have a nice big colour gps it should be easier to hit the turns faster.
I also took too much water, I had a 3ltr camelback and 2 water bottles on the fork legs. The water bottles never got touched as there were so many drinking opportunities from streams etc ( I was using water sterilising tablets).
The only other change I would make is the food I was eating. Coconut oil eaten raw was amazing rocket fuel. energy bars and cereal bars were just too hard to get down without gulping water.
The only section I didn't like too much was the loop around Dunnerdale fells, bit of a boggy mess and riding through long grass, slow going. The rest was amazing, can't wait to go again.
@AlasdairMc - Cumulus Ultraligh Sleeping bag 620g, Klymit inertia x Lite 173g and an Alpkit Hunka bivi 388. Barring that I only took usual spares and more food. Additional weight I guess I should count the wildcat handlebar harness at 140g and my ortlieb 13ltr drybag, though not sure how much it weighs.