This story sees the first on-screen appearance of Mrs. Bright, much spoken of previously in earlier episodes, but never actually seen.
Although Mrs. Bright's pet name for her husband, "Puli", may refer to a species of Hungarian sheepdog, it's more likely to be Tiger or Panther in Tamil or one of the South Indian languages.
Regarding the Bura suicide, Morse says he spoke with a Bura acquaintance, a Rhodes scholar and rugby player named Clinton. This is a reference to U.S. ex-President Bill Clinton, who won a Rhodes Scholarship to Oxford University and attended classes there in 1968 and 1969. Clinton also played rugby while at Oxford.
The vet reads Morse a crossword clue he is struggling with: "Slaughter a horse, then worry about it." Morse provides the answer: "Carnage". The first word of the clue is a synonym of the answer, and the remainder is a formula for constructing it: Begin with a synonym for 'horse' ("nag"), then take a synonym for 'worry' ("care"), split it in two ("car" and "e"), and wrap it around ("about") the horse synonym -- thus "car" +"nag" +"e" or "carnage".
In discussing the 'derelict' who died from the drugs overdose, Morse says, "A soldier, possibly" and DeBryn replies, "Known Unto God." "Known unto God" is a phrase devised by Rudyard Kipling and used on the gravestones of unknown soldiers in Commonwealth War Graves Commission (CWGC) cemeteries.