William Shanahan is an agent with MI6. Jack Gawain is a member of the paramilitary Ulster Defense Association.
The two protagonists (I definitely would not mislead by calling them heroes) of this series do not know each other when the three recorded adventures start and when they do meet, they most assuredly do not care for each other. As time goes by and trouble gets heavy they will acquire a very grudging respect for each other but they are a long ways from being drinking buddies.
We are shown straight off how arrogant and full of himself the 'leader' of this partnership is when we are told, "Captain William Shanahan always thought of himself as the gold standard of the SAS. He considered himself the prototype of what every secret agent in MI6 should be. At six-foot-two, two hundred and ten pounds of surgical steel and sex appeal, he was the ladies' pet and the men's regret. He had religiously followed a rigorous training schedule and personal diet over the course of his lifetime that gave him an imposing athletic build featuring a washboard waist and perfect musculature. Whenever he had any concerns or doubts about undertaking a difficult assignment such as this, one look in the mirror quelled his apprehensions."
His history is summed up nicely with, "He enlisted in the service in order to take part in Operation Desert Shield in 1991, and when it escalated to Desert Storm, he volunteered for the Special Air Service. He served with them for his first tour of duty before being transferred to the Special Boat Service. He spent his second and third tours with the SBS before being dispatched to Afghanistan for a fourth tour. It was during that time he was offered and accepted a position with MI6. It was then that he could look back and say he had sold his soul in the process."
His desired future is also stated when we read that, "He had been motivated by a lifelong desire to have a family, a wife and children of his own. MI6, the Secret Intelligence Service, had been his universe for nearly two decades. He had worshiped at its altar, been one of its most devoted acolytes, and gave it place over his life. After this job, he would call in his markers and get the desk job. After this he would find a wife, reclaim his life, and live happily ever after."
On the other side of the prison bars, for that is where Jack Gawain is when we first meet him as Shanahan is sent to size him up for the upcoming mission, we have the 5'9" 180 lbs Gawain. "Although he was fairly smaller than Shanahan, he was thickly muscled which suggested a lifetime of powerlifting. His black hair was trimmed, his skin was pasty from lack of sunshine which accentuated his coal-black eyes. His eyes brimmed with energy as he stared at Shanahan, his lips curling just short of a perpetual smirk." That lopsided expression will prove to be a frequent visage.
Gawain got his anger and motivation at an early age during the Troubles in Northern Ireland when members of the IRA mistook his father for some else, shot and killed the man, and raped and killed Gawain's mother. When he was old enough to join he became a member of the Ulster Young Militants and later moved to the Ulster Freedom Fighters before becoming a part of the loose federation known as the UDA.
When Shanahan noted that Gawain was nicknamed the Hacker, he asked if the man was good at computers but was told that Gawain had "a reputation for beating his victims during interrogations with the backs of his blades. When the handle shifts in his hand, either accidentally or on purpose, he winds up hacking into his victims. It leaves most of them grievously wounded, maimed or dead."
These are the two gentlemen, along with a couple of very capable and extremely dangerous women who will join with them as needed, who are asked to save the world.