"He then spent several months going to and fro to see her at Kensington Palace," Clarkson says.
Pink Floyd have been getting a lot of attention lately.
For 30 years, it has remained one of the most intriguing of royal secrets.
The author has an impressive source to back up his claims - the police chief who questioned Bindon, who was later acquitted.
Retired Chief Supt George Mould says that he was approached by MI5 officers after Bindon, who had gone on the run after the killing, returned voluntarily to face the music.
Whenever possible, though, they fly their chopper — both are qualified pilots — to their 18th-century country home of honeyed Cotswold stone near Corsham, Wiltshire.
Seven-bedroom Middlewick House sits in fields, woodland, paddocks for a menagerie of horses, miniature donkeys, pigs, dexter cattle and chickens, and a delightfully rambling garden.
The pair are extremely close - Ella, 23, often stays the night at her 24-year-old boyfriend's Chelsea flat.
But with Taseer planning to leave London, where he has been working as a trainee journalist at Time magazine's London bureau, for a new post in Turkey, there were fears they might be parted. "He's been telling friends that he and Ella will set up home there," says one of his circle.
"They asked Mould not to mention the Margaret affair if it came up to anyone and wanted to know if Bindon himself had raised it," says Clarkson.