Well, 20mph unless you have a raging tailwind, is not a steady pace, I’d suggest that’s probably putting some people off. If you’re new to it and want a steady ride I’d suggest 17mph/18mph for 2hours depending on where you live and HOW steady you want.
I have to press on pretty hard to do 20mph for a couple of hours, certainly wouldn’t want a pint in the middle! And it’s hard to do that with a group cus there is always one that is struggling a little.
And my comment about cadence was that one persons steady 17mph ride could be at 90rpm and another persons at 130rpm.
Edit: ah Cheshire, ye, I live in the lakes so I’m used to sh1t roads and grippy hills. Maybe more achievable but still I’d say that quoting 20mph as steady would put a lot off.