Deep in the credits under "Camera Trainees" can be seen Alfie Oldman, Gary Oldman's son. He's worked on several movies that Gary starred in.
In the books Jackson Lamb is said to resemble Gary Oldman's Remembrance (1982) co-star Timothy Spall "gone to seed" and "with worse teeth."
"Moscow Rules" and "London Rules" are fictitious, the second made up by Mick Herron (on whose book of that title the series is based) as counterpoint to the first, made up by John L Carré.
In the books, the Peter Judd character is clearly based on (then) future British Prime Minister Boris Johnson. In the TV series, this connection is far less obvious.