I could tell from one or two prior series that they were cutting back on Sallis' involvement as Clegg in the show, most likely due to age and health. In this mad dash to watch the whole show before the final episode I reached Series 28. I don't know if anyone has noticed it, but from The Second Stag Night of Doggy Wilkinson to halfway through the series, Sallis' voice is very noticeably different. It's like a low, frog in the throat/cold sounding. Also, noticed a bit of slurring (not really sure what to call it). Was Peter of ill health during that time and recovered when they got to the middle of filming the series?