So it's going to get dark at 21:06. That's less than an hour after we set off. Most of the ride is on unlit roads so I will definitely need spare batteries. Weirdly Sunrise is at 05:09 the following day... so I've got 8 out of the 10 hours riding in pitch black.
Apparently there are quite a lot of bats
Here is a lovely description of riding the event
That's all at the moment.