It started 49 years ago - and I can't think of one.
So is there one - and if not what is the nearest to one?
Has British Commercial Radio Ever Produced A Comedy Series?
They have if you count them as part of a DJ's show. I wasn't a huge radio listener but still remember Captain Kremmen created by Kenny Everett and also on Capital but a bit later in the 80s Chris Tarrant did a daily or weekly reading of tales from Greyfriars School, which I remember was very enjoyable. So I wouldn't be at all surprised if Capital did a few more comedy airings I didn't hear. As for 30 minute sitcoms with a full cast, I very much doubt any commercial radio station has attempted that, and I suppose why would they, that's what we pay the Beeb for.
It's definitely rare, but just to say there have been a few. In terms of recent things, Union Jack Radio (on DAB) produces some; and Absolute Radio has tried a couple of formats (most recently Rockanory: https://planetradio.co.uk/podcasts/rockanory/)
Thank you Alf and Mark for your excellent replies. I was initially disappointed that my posts got no response but maybe I was hoping too much for immediacy. What you have done is more than made up for it as I wanted it to go out to wider thought. Not for just me. Alf - when I wrote my post, I did have Kenny in mind. The idea - I nearly mentioned it - that he was the closest they have got to it. The World's Worst Wireless Show etc - and actually in radio terms (not so sure about his TV stuff) an absolute innovative legend like Joe Meek was to music, say. Crazy, yes, but brilliant.