Well, I can remember What's My Line? very well. It was essential Sunday night viewing. It ran from 1951 to 1963 and was hosted by Eamonn Andrews. The leading panellists were Gilbert Harding, David Nixon, Lady Isobel Barnett and Barbara Kelly.
There were a number of comparatively unsuccessful revivals in the 70s, 80s and 90s.
Having said all that, I don't remember a speedway rider on it, which is not to say there wasn't. The most famous occupation featured was, of course, the saggar maker's bottom knocker.