On one of our (rare) Class 4 jobs we can roll pretty much from Hemel Hempstead to North Wembley before having to touch the brake, given a clear road.
I remember being told by a driver I knew years ago, that he had been driving an up express and that the engine had failed to restart after shutting down for the neutral section at Bourne End ~26 miles from Euston. He said that he rolled all the way to a red signal halfway down Camden Bank. Apparently he found using the SPT to report the engine a failure at Bourne End, to Euston PSB rather amusing.
Wasn't it the damage caused by this incident that caused the closure of the avoid?
eastwestdivide previously shared a very similar anecdote, if not the same one!
Did he know Ron L. too?
Way back when I started reading railway mags, probably late 70s, there was one of the "train performance" columns, with speeds and logs etc, which I'm pretty sure had a section about a southbound WCML electric fail at full speed (no power) somewhere ridiculous like Tring, and the gradients and momentum carried it all the way in to Euston.
Tring's about the summit of the Chilterns round there, so it seems quite possible, especially in view of Rugd1022's comment above.