When Diana was 15, her father secretly married a glamorous, younger woman. The future princess and her stepmother became locked in a bitter rivalry. But it ended with a surprise friendship.

"Raine, Countess Spencer, died peacefully at her home in London on 21st October, 2016, after a short illness," the family said in a statement. Erin Hill is the Senior Editor, Royals at PEOPLE.

T his Mayfair townhouse is pretty special: formerly owned by Princess Diana’s father and his second wife, Countess Raine Spencer, it was frequently visited by Diana herself. The house hit the ...