@Cloister
I’d definitely recommend two lights, whenever and however possible. A bar-mounted for the trail ahead and helmet-mounted to aid your view of the trail ahead, help provide a better perspective by eliminating shadows (or even highlighting them in other respects) and double the power means if one suffers a problem then you’ll have a second to ‘get you home’. I’d say essential for unfamiliar terrain, even if it’s not mandatory.
I remember one of the gang hiring a set in 2016, Wi(n)dowmaker I think it was. I’m fairly sure light hire is available again this year for others wondering.