Charles Garrett is an anti-terrorism expert with Special Branch.
When terrorists began to strike close to home, the British government created a small group of agents into an elite bureau called PACT, or Punitive Actions, Counter-Terrorism. Tasked with working closely with the Special Branch but also able to share the resources of MI-5 and MI-6 as well as the various military intelligence groups, this group was designed to be Britain's counterterrorism enforcement arm. Empowered to do what it takes to keep the country safe, the director chose the best people for each job. Unlike Special Branch whose job it was to arrest terrorists, PACT was empowered to eliminate them.
Heading PACT was an experienced Brigadier named Bleke, a former director of operations for MI-6. Since PACT was meant to be largely off-the-books, it created a front called the Diversified Corporate Facilities. Government funds could be funneled into this paper holding company and used as its director saw fit.
For the enforcement with extreme prejudice duties, he picked Garrett, an agent who had worked undercover in Northern Ireland before the murder of his wife ended that assignment. Now Garrett lives for his job, having little else. And he shows again and again why he is the very best at destroying the enemy, no matter what it takes.
This series has two authors listed as writers. They are the same man. The first two books were published under the pseudonym of Donald Severn but the latter two were under the real name of the author, Frederick Nolan. The first two were released in the US as well as the UK. The latter two probably were not released in America.