Did Brian leave the series first time around because of a row with Bill Owen? I was reading an article from the 80s which stated that Bill Owen and Brian Wilde didn't get on.
Have had a quick skim of Andrew Vine's book. It was not specifically a row with Bill Owen. Wilde did not get on over well with anybody and was generally critical of many aspects including the script. He did rather naively tell a reporter that there was some friction and that got published which did not please rest of cast and crew. This is all in a chapter "Loyal but Disagreeable" which tells its own tale. Wilde just basically decided it was time to move on. Quote: 'He was also restless, saying, "Being an actor, life should be varied."'
Interestingly, one of the first thoughts for a replacement was Fulton MacKay, also from Porridge. That would have been interesting.