Had a roadie come up behind my nine year old in full kit last year and berate him for being in the way. There's too many people to do it at speed or have 'give way' rights for being faster and I told him as much.
There's always one, isn't there? Surely a roadie in full kit is missing the point. He can ride any time he likes, on the road, can't he, if he's that keen? Or is he actually too scared to do that - all the gear and no idea?
I did the Leicester one, and it took me about 90 minutes to do what ended up as about 9 miles (bit of a detour). There were places where you just had to sit back and wait, because a little kid was all over the road, or someone stopped suddenly on a steep bridge. Add in that I was on a borrowed unfamiliar bike, and there was no way I was taking any chances. In fact it wasn't all that relaxing - traffic in car form was just swapped for traffic in bike form.
But I can see that a novice or newbie, or just the occasional family cyclists, would enjoy it.