Interesting snippet from the Clement/La Frenais book "More Than Likely" that I have just started reading, about Harry H Corbett.
I think most know that the H (stands for Hennyfing) was a complete fabrication by Harry to distinguish him from Sooty's "hand", but it went awry one time when he was up for an OBE, but somebody forgot to include the H in his name and it went to Harry Corbett, much to his surprise and delight.
But I digress. So, "Mister Aitch" was an idea of Harry's he wanted our heroes to write; BUT Harry interfered with the storyline so many times, it became a mess. They walked away from it and the series died on its arse after the first episodes and it seems they have all been wiped, so we won't be able to judge for ourselves.
And it seems Mr HH Corbett is not the only one who will not leave it to the experts - they follow that up when they were summoned to Hollywood to work on Will Smith's "Amulet", and much the same happened there. From what I can gather, it is still "in production", some 10 years later owing to Smith's interference.