The book identifies Jacqui Chan, a former model and dancer, as his first real love.
It was apparently felt that if this – not the bizarre love triangle – emerged it would cause scandal at the royal wedding.
Lord Snowdon then even briefly considered having Jeremy Thorpe, later to be the leader of the Liberal Party, as his best man but a cloud over the politician's sexuality ruled him out, too.
Lord Snowdon seems to have agreed that there should be no "no-go areas": he has been willing to talk about his troubled marriage, his bitter rift with one of Princess Margaret's closest friends and other controversial areas of his occasionally bizarre life.
For many, the book's greatest interest will be in Lord Snowdon's tangled – and at times tragic – love life.
The book will also scrutinise the 20-year relationship that Lord Snowdon pursued with his mistress Ann Hills.
It ended in tragedy when she committed suicide on New Year's Eve, 1996: she had been lonely over Christmas and had telephoned her lover to explain her unhappiness.
Today Mrs Higson is 48, a married mother of five and lives in rural Somerset.
Yesterday, she confirmed the claims in the new book, but insisted that she did not want to say anything more. Shortly before his first marriage, Lord Snowdon used to visit the Frys regularly at their home, Widcombe Manor, Bath.
In a further twist, the book details how Jeremy Fry, who is now dead, had even been due to be best man at Lord Snowdon's wedding to Princess Margaret, but he stood down late in the day due to an alleged illness.
In fact, although by this time it was not known who had fathered Mrs Fry's unborn child, Mr Fry had been convicted of a "minor" homosexual offence and fined £2.
The book claims that Miss Fry was conceived during a weekend when alcohol and "poppers" – amyl nitrite stimulants – had been in ready supply.