Mark Savannah is an agent with MI6.
That is not an unusual statement to make considering this compendium but in the case of Savannah, it is very odd. The reason is that he is not British; he does not have British citizenship. Or rather, he didn't until he became Mark Savannah. Before that transition, he was Barnett Cooper, an American training to be a psychiatrist. So the road that took him from America, down to Argentina, and then to Oxford and finally service with the SIS is an unusual one, told in the first couple of chapters of the first recorded adventure.
Savannah had been a youngster having definite father issues with a strict, demanding parent for whom he had little respect though a good need for acceptance. When that parent was killed in the infamous incident in Mogadishu, Somalia, his inner turmoil became more intense. "The presence of a domineering father, then his sudden absence, a busy mother looking for a partner she could rely on, and his own strong and introverted character, had prevented him from coming to terms with adolescence quietly and gradually. Instead he chose to immerse himself in extreme sports in order to test his limits and, above all, not to hear the silent scream of his solitude. It was as if he didn't care about dying, and this continuous daring consumed him but frightened him to death." Plus, we are told "he would finish Medical School and get his M.D. and afterwards his PhD. He had a natural gift for science and wanted to show the world that he lived without compromise; his mother had given him the money he needed, and he would repay her in the future for allowing him the freedom to choose his own life."
So, how did such a man find himself in London applying for a job he had never thought of before? Well, for that you have to read the tale yourself as it will decidedly affect the many things, a good number of them quite unpleasant, that came after.