I see the North side of Holme Moss mentioned – in my misspent yoof I used to see how many cars I could overtake down there on a Sunday morning. Such foolishness is not recommended and well behind me, but it is, much more recently, the site of my fastest solo recorded speed, 57mph. There must have been a tailwind.
Fastest tandem speed is identical, on the Rosneath peninsula, whilst trying not to melt the blocks. We now have a drag brake
NB, I noted only last week the Holme Moss descent features a Strava segment named “this is where I broke my shoulder”, or somesuch. Never try to go faster then you’re really comfortable with, don’t succumb to peer pressure.