On the previous incarnation of this forum I found details of an excursion from Paddington that toured the Bristol area in the early 60s. Much of the route that day no longer exists.
I've now found details of another such tour on 21st July 1963. https://www.sixbellsjunction.co.uk/60s/630721lc.html
Scroll down and it shows Clifton Down to Mangotsfield took just eleven minutes!