Looking at the RatRace (the crossing) video doing the rounds on FB, anyone reckon its possible on a CX…seems like lots of road and bridleways to me, but could be wrong?

2 ladies rode CX bikes the year I did it. As you say there is a lot of road. Some of the bridle ways were through muddy fields, the ladies had to stop a lot to clear gears, brakes etc. They were slow on some of the rough downhill sections and suffered from sore arms/wrists(old school mtb problem)
So, yes it is doable but not comfortable! CX/gravel bike wouldn’t have enough gears for me!
I rode my Blue Pig but wished I’d taken my old Kona, My back was wrecked by the end 🙄