Flamboyant, extravagant and always hungry for publicity, the self-styled king of Mustique ensured that everyone knew of his unique place in the Princess’s life.

But as his lifelong friend, I knew he planned to reveal far more in the uncompleted autobiography I was working on with him just before he died, aged 83, in 2010.

By then, Margaret, too, was dead, so no subject seemed off-limits — from tales of cavorting naked in front of her to the fact that he’d once hidden behind an arch to check whether she was indeed having sex with a man she’d just met.

Their friendship, he said, hadn’t fully ignited until 1954, by which time Margaret was at the height of her beauty and he’d become the favourite of her escorts.

He presented The Home Show in 1990 and The Gardening Roadshow in 1992-1993 for Thames Television, amongst several other programmes. In the late 1970s, Llewellyn recorded an LP called Roddy.

Yet that long-forgotten party was the start of what would become an intriguingly close and enduring relationship between Margaret and Colin — the heir to Lord Glenconner and then one of the most eligible bachelors of late Forties’ high society.

Lord Snowdon, 46, will be required to find alternative accommodation. In a statement the Archbishop of Canterbury, Dr Donald Coggan, who is in the West Indies said: "One hopes that every understanding will be shown to the Royal Family at this time of distress." The Princess was granted a decree nisi on at the Law Courts in London.

Six weeks later the decree became absolute, marking the official end to the marriage.

He would later provide an entree into a decadent new world, far removed from the one in which she grew up.

Thanks to him, she ended up mingling with a louche set of stars, multi-millionaires and aristocrats on the Caribbean island of Mustique; and it was Colin who introduced her to her lover, Roddy Llewellyn, then gave them a love nest for their scandalous affair.

He regularly lectures, appearing at venues including the Retirement Show at Olympia, Glasgow and Manchester (chairing question and answer sessions), Dobbies Garden Centre ("Inspirational Ideas for the Garden"), Hereford Cathedral ("Interesting Ideas for the Garden"), Malvern Spring Gardening Show ("Who are better Gardeners - Men or Women?