First of all, @citizenfish, I have to say that your book on the history of the year record (
https://www.v-publishing.co.uk/books/categories/biographies/the-year.html) is really fascinating and impressive. I have just finished it and an in awe of the riders as well as your work.
I cannot stress enough the importance of BALANCE when looking into this history. Random snippets of internet do not tell the full story. Reading across the entire press of the time, the Raleigh archives and accounts(searching for payments) and family interviews give a broader view of what actually happened. This is what it took me years to get to the bottom of it, not ten minutes of internet search and a bit of cut and paste. The real story shows two riders fighting each other for miles using everything from sleep deprivation to drafting to get them, both goaded on by their relative team managers. THIS is what pacing means. The final judgement on ending it specifically mentioned the team managers retreating.
The internet myth (zombie factoid) is that they got up, sat behind a team of riders for 12 hours 365 days a year and then went home for a bath. This myth fails to explain where these rides came from? Who these "teams" were given that the industry in the main sponsored individuals and road racing did not exit in the UK. Who paid them given that Raleigh's accounts show no payments? And if they were not paid how these men were recruited as the press at the time shows nothing? And I've found nothing in the National Cycling archive when going through club/RTTC records etc.. of 1939?
Secondly, I find it really striking how little we know what really happened in those crucial summer months of 1939 despite all that hard work. If there really was no team of paid cyclists or organised motor vehicles used to break the wind for Tommy Godwin (that's how I would intuitively understand the concept of "pacing"), the big question really is how he managed to crank out these incredible miles.
Sleep deprivation IMHO can only be part of the explanation, but I find it hard to believe that this in itself made the difference, as he had already four to five month with long rides and relatively little sleep in his legs when the crazy months started.
The black box between June and August, where Tommy rode 255, 277 and 238 miles per day respectively, also puts Steve's perfornace into perspective, and highlights Kurt's achievement. A back of the envelope calculation shows: if you assume Tommy had ridden daily averages of 215 miles in June, July and August (16 percent less than he actually did, but still 20 percent more than on an average day between January an May), his yearly milage had come down to 71235 miles.
Further assuming that Steve had not been hit by a moped and had been able to increase his daily average to 200 miles in April and May, 215 in June to August, 200 in September and October and 180 in December, his annual milage had been about 73000. That's 1800 miles higher than Tommy without his super-human summer, but still 3000 miles below Kurt, who achieved his mileage without these crazy days in the summer.
That's only 4 percent less than Kurt, but getting this last extra uptick in mileage probably takes a disproportionately large amount of extra effort, in particular due to the need to sleep. Maybe that's the difference between hilly England and flat Florida, having a camper van and Alicia or not.