Wolf at the Door by Jack Higgins

On Long Island‚ a trusted operative for the president nudges his boat up to a pier‚ when a man materializes out of the rain and shoots him. In London General Charles Ferguson‚ adviser to the prime minister‚ approaches his car on a side street when the car explodes. In New York‚ a former British soldier taking a walk in Central Park suddenly has a gun in his back. And that's only the beginning. Someone is targeting an elite unit known as "the Prime Minister's private army."