Doctor in the House S04E26 - Blackmail

Professor Loftus is near to receiving his knighthood when he hears that Professor Mincing from Highcross has also been considered. Having suspended Dick for cooking the books for the hospital bar, he reinstates him when Dick gets him membership at his club. Unfortunately this is all seen and recorded by Professor Mincing so, to avoid further suspension, Dick and Duncan, disguised as window-cleaners, set out to retrieve the tell-tale tapes.