Joanna David who plays Susan in this episode is the aunt of Laurence Fox who plays DS James Hathaway in the Lewis series.
Some viewers may recognize the distinctive gates drive and 3 arches at the exterior of one of the houses "Byres Hall", the home of "William Bryce-Morgan". It was also used in the Lenny Henry comedy series "Chef", where it doubled as his character's "Chateau" restaurant. The building is in fact a real house, which is actually Nether Winchendon House, Nether Winchendon, Buckinghamshire.
There is an anachronistic error made in the spin-off prequel series "Endeavour", S4e3, "Lazaretto". In that episode Mr. Bryce-Morgan dies and his widow speaks tersely with Morse.
This episode of "Morse" appears to be the first time that Strange calls him "matey", up until this point he's always called him Morse. However, in "Endeavour", Strange always seems to call him "matey". The change is clearly due to their change in the workplace dynamic, to superior and subordinate.