The Quiller series is one of those cold war delights. A book series about an undercover british agent who goes very deep undercover behind the iron/bamboo curtains. One turn of phrase used is "throwing the ferret down the hole to see what it can find out". He's often completely cut off from any backup and has to rely on his wits and ability to evade the opposition to survive and escape.

He's the anti-James Bond.

Quiller Series (Adam Hall) timeline - Lists the publish dates of the novels.

The Berlin/Quiller Memorandum, 1965
The 9th Directive, 1966
The Striker Portfolio, 1968
The Warsaw Document, 1971
The Tango Briefing, 1973
The Mandarin Cypher, 1975
The Kobra Manifesto, 1976
The Sinkiang Executive, 1978
The Scorpion Signal, 1979
The Pekin/Peking Target, 1981
Northlight/Quiller, 1985
Quiller's Run, 1988
Quiller KGB, 1989
Quiller Barracuda, 1990
Quiller Bamboo, 1991
Quiller Solitaire, 1992
Quiller Meridian, 1993
Quiller Salamander, 1994
Quiller Balalaika, 1996