A Girl's Best Friend is the 1552nd episode of The Bill.
PCs Klein and Quinnan finds the body of a man who has died of a heart attack in a car. When delivering the man's personal effects to his wife, Quinnan is mortified to find they include a gift to the man's mistress, a woman named Alice. Trying to do a good deed, Quinnan resolves to deliver the gift to its intended recipient, but things become much more complicated when his wife Jenny Quinnan discovers the gift and thinks he's having an affair, and CID discover that the dead man is wanted by Interpol for diamond smuggling.
Meanwhile, Supt. Chandler wants everyone, including DCI Meadows, to film a "mission statement".
- Andrew Paul as PC Dave Quinnan
- George Rossi as DC Duncan Lennox
- Natalie Roles as DS Debbie McAllister
- Gary Grant as DC Paul Riley
- Ged Simmons as DI Alex Cullen
- Steven Hartley as Supt Tom Chandler
- Rene Zagger as PC Nick Klein
- Lisa Geoghan as PC Polly Page
- Ben Peyton as PC Ben Hayward
- Simon Rouse as DCI Jack Meadows
- Raji James as DS Vik Singh
- Ben Roberts as Ch Insp Derek Conway
- Matthew Crompton as PC Sam Harker
- Tony O'Callaghan as Sgt Matthew Boyden
- Suzanne Maddock as PC Cass Rickman
- Colin Tarrant as Insp Andrew Monroe