Matt Flynn is an agent with the HSA.
We are told in an introduction to the first recorded adventure that that organization, the Homeland Security Agency, was "established by the Home Office, the brainchild of minister Sir Raymond Deacon. Its unofficial motto is: 'Fight Fire with Fire', and it is staffed by agents operating under similar rules of engagement as the UK military. It was set up to combat the changing threat faced by UK security forces from terrorists, criminal gangs, ruthless organisations and individuals. Terrorists who no longer appear in the open, but integrated themselves into local communities; criminal gangs who use open borders and the web to traffic guns, drugs and people; and rich organisations and individuals who believe they are above the law. The headquarters of the agency is located at a secret address in London. There are other HSA offices at various centres around the UK."
When we meet him, Flynn is looking especially scruffy but this was on purpose as he was undercover working in a construction crew tearing down an old factory; his purpose being to become friendly with a group of Armenian workers who were smuggling heroin into the UK. Normally drugs was not the target of the HSA but this group used the proceeds of the sales to finance terrorist activities in Europe and that make it of interest to the HSA.
He is annoyed when he is pulled off for a new assignment but Flynn is too good to balk too much when given an order by Rosie Fox, his boss at the HSA and occasional partner in field work; that and doing deconstruction work is a far cry from the kind of action that he got from being an HSA operative. Flynn loves a challenge. Besides, he actually likes and respects Fox as both of them have plenty of experience and both live for their work.