Old but still timely: This 2005 CSO article on the six things you should know about executive protection. An excerpt:
Terrified, haggard and frostbitten, Karen McMullan refused to give police the details of her ordeal until she knew her husband Kevin was safe. Twenty-four hours earlier, men dressed as police officers had talked their way into the McMullan's home. Once inside, they held a gun to the head of Kevin McMullan, the assistant bank manager for Northern Bank in Belfast, Northern Ireland, and explained that he would help them carry out a daring robbery. To ensure his cooperation, they kidnapped his wife.