Afraid my best is a lowly 28 miles ( Haibike sduro 27.5/ 400wh)(All in high setting)
It did include 4 big climbs around Sheffield Reservoirs ( one a dead end), lots of boulder strewn paths and one long slog through rutted peat bog...so I was very impressed it stayed course.( Had a bit left in battery at end but not so much in legs)
Putting ride in perspective , imagine Winnats pass on single track for 2 of climbs.
Perhaps we should add a caveat to original question.How much further did you get because of the battery energy you used..
Well I couldn't have done 2 of climbs on route ( they,d have been walked ??) So battery made it possible to do ride or cut time to a third .( Route would take me 6 hrs plus on none e bike rather than the 2 hrs 14 mins ????)
Best view on that ride.