Royal Slaughter

Jack Slaughter is an agent, but there's nothing secret about him. He is a force to be reckoned with.
His new assignment is an encore performance. Five years earlier, Jack was sent to London to protect Queen Sophia from assassination. In the process they'd fallen in love, but restrained themselves. She was the queen, and he was a lone killer.
Now he must go back, save Sophia from her insane brother, Prince Laurence, who may have the entire military behind him.
Jack against the British Army. Sounds like a fair fight to him. And he's ready to do whatever it takes to get the job done.