Britain's Earl Spencer says his late sister Princess Diana's fame helps with his career.
The historian and author believes observing the global recognition his sister - who died in a Paris car crash in 1997 - experienced helps "humanise" the people he researches for his work.
Discussing his new book, 'Killers of the King: The Men Who Dared to Execute Charles I', he said: "When your big sister becomes arguably the most famous woman in the world, you realise the absurdity of fame. It really helps as a historian. They're still human beings.
"One of the most moving passages in this book is the king, knowing he's going to be executed the next day, saying goodbye to his eight-year-old son and 13-year-old daughter. In that scene, he's no longer a king."
Charles previously worked on the 'Today' show as a correspondent from 1986 to 1995 and says his sister was able to reduce network executives "to jelly" with her presence.
Recalling a time Diana visited him at the NBC London bureau, he told the Wall Street Journal: "[It was] at the peak of her global fame to take me out to lunch. All these hardened NBC hacks were reduced to jelly."