I too, did it with Nigel Craven one year, and struggled to keep up with him.
It's probably the hardest (and most hated) race I've ever done: the ascents are steep and the decents simply not runnable in quite a lot of places. You really need to put in the legwork beforehand as even though it's only 16 miles, it's not a race you can turn up to unprepared.
From memory it's partially flagged, but gets a big(ish) crowd so there will be people to follow.
Anyway, I've entered this year's race so I'll be there.