George Barclay is a private investigator.
He prefers to call his occupation that of "commercial investigator" but invariably someone will respond with a sneer calling him a private detective and not being too friendly about it. Which is strange considering the number of cases he has solved, saving insurance companies a lot of money and helping authorities in the process.
Barclay is definitely not a spy and has no desire to be one. He is quite happy doing what he is doing and since he does not spend any time bemoaning a lack of clients or having run-ins with his local bank manager, as well as the fact that his secretary seems content enough with working for him and not grousing about back page, we have to conclude that he is successful at his job. Taking into account that most of his work seems to be for insurance companies, we should conclude that as Barclay is a very sharp individual, he charges enough to make it worth his time.
However, though Barclay is not a government operative, he definitely gets into situations where one could mistake him for a secret agent. For one thing, while his home patch is London and he is quite happy there, he does find himself involved in cases which take him to various locales on the Continent, either chasing after or being chased by someone. He even makes it as far south as the lower tip of Africa, quite a ways from the Thames.
Then there are the people he has to go up against. Most notably the Komeski, an international criminal organization with hooks into all sorts of nasty endeavors. This is a team of thieves, blackmailers, and killers that come from all nationalities to work for one group, stealing and extorting and murdering without worrying a bit about borders.
One time he is actually officially hired by his government's intelligence community. Most of the other times it is someone even more powerful asking for his help - wealthy insurance companies.
Barclay remains for the most part on very good relations with the police forces of most countries he visits. He has worked with several a few times over the years, showing he is by no means new to this business. He even has an inspector at Scotland Yard as his best friend and drinking buddy.