Jacques Duvall is an agent with the British Secret Service.
MI6. SIS. Call it what you want. It's the intelligence agency that has the Lego building on the Thames. You've heard of it.
It is run by a fellow named 'M'. No full name given and none needed. Use the letter and everyone knows who you are talking about.
He runs a special section inside the organization that has specialized operatives trained to handle any sort of emergency and authorized to eliminate enemies as he or she sees fit. These special agents are given code-numbers to identify them.
Jacques Duvall is 006.
Duvall is a mutt. That is what Françoise Dupree calls him when they first introduce each other. Father was British. Mother was French. They fell for each other immediately and Jacques was the result. "My father was a British Intelligence agent for Her Majesty's Service and he got me in when I was young, right out of school. You know what they say, 'Like father, like son'. I worked my way up over the years and I've been doing this kind of work for a long time now."
The Dupree mentioned above is a French intelligence agent who works with Duvall on the first recorded adventure we have of him; product of a French father and an Iranian mother so she adds Farsi to the language mix the couple have. They get quite close in that adventure and remain so for all the adventures we have of Duvall.
Just like other agents with a designation starting with '00', Duvall definitely get around the planet on his assignments. Unlike at least one other such agent, Duvall is a one-woman man from the moment he meets the lovely Dupree and it is a good thing, too, because she is also a very, very capable woman.