Antoine Springer is an agent with the UNIT.
Now, it is important to point out that in some places, the organization is known by that acronym while at other times it is UNI. What exactly either officially and for certain stands far seems to be up for debate. One place we are told that UNI was the abbreviation for United Nations Intelligence but a different place led me to believe that might have been one member's attempt at a name. Then I read a different name, United Nations Intelligence and Tactics, hence UNIT.
Either way, the more commonly used name for the group is the Agency which, considering several members are former employees of the CIA, also frequently referred to as 'the Agency'. That has to be confusing.
A middle-aged woman named Rose Appiah created the UNIT. She started out working with MI5 heavily involved in the last days of the Cold War. Then when that came to an end with the fall of the Soviet Union, the emphasis turned to both the War on Terror and the War on Drugs. It was at that point that Rose felt her allegiance wane and she quit, took a gap year, and came back to found the organization which she describes as "a globally independent spy agency, free of any affiliation to countries".
As stated, Springer is one of the UNIT's operatives and a very respected and valued one. Before he came to work for Rose and the UNIT, though, he was - and here it is a bit confusing - someone else.
I believe that someone is a CIA agent named Dwayne Carter, married to Kerrie and father to young boy named DJ. The confusing part is the fact that someone comes to tell Kerrie that Dwayne was killed in action. Then we find out Antoine regrets the loss of his previous life but there was no other choice (why? No idea).
So, apparently Antoine used to be Dwayne.
But there seems to be two Antoine's. One is a dangerous and effective agent who get the job done and then finds his relaxation wherever he can. The other is an agent who has relaxation (i.e., the opposite sex) as his one and seemingly only priority.
Beyond all that - things gets even more confusing.