Royal Photographer Looks Back at Throwback Pics of King Charles 'Having Fun' with William and Harry

"People say he was a cold father, but I never saw it. I always saw him having fun with them," royal photographer Arthur Edwards MBE, author of the new book Behind the Crown: My Life Photographing the Royal Family, tells PEOPLE. "They were always teasing him, we call it 'taking the mickey.' "

"We used to go skiing every year with them. The photo call we would start, William had put his arm around his father and his father would tickle his ribs. It was great fun. They were a very strong family," he says.