Royal wedding speculation grew yesterday after claims that Buckingham Palace has 'cleared its diary' for a June announcement of an engagement between Prince William and Kate Middleton.

According to well-connected former editor and author Tina Brown, aides plan to announce on either June 3 or 4 that a wedding will take place in November.

Miss Brown was a personal friend of William's mother Diana and has published a well-received biography of her.

She said the hint had come from an anonymous - but impeccable - royal contact.

'A high-placed source in royal circles tells me that two days in June have been mysteriously blocked out on the palace diaries - June 3 and 4,' she wrote yesterday in a blog on her news website The Daily Beast.

Dating for seven years: Kate Middleton and Prince William

'They suggest this is a likely date for the engagement announcement at last of the 27-year-old Prince William and his patient squeeze, 28-year-old Kate Middleton.

'If so, a wedding itself would probably follow in November, like the wedding of Queen Elizabeth II and Prince Philip, who married at Westminster Abbey that cold, damp November day in 1947.'

British-born Miss Brown, a former editor of Vanity Fair, goes on to speculate that a June engagement and winter wedding would 'make sense all around' in that it would come after the General Election and take place before William took up his first three-year posting as an RAF Search and Rescue pilot.

She added: 'The Queen and Prince Philip, moreover, are approaching two landmark moments: Philip will be 90 in June 2011, and the queen celebrates her diamond jubilee - 60 years on the throne - in February 2012.

'Their closeness to their grandson, especially Philip, makes them eager, I am told, to see William settled in matrimony.'

Contacts: Diana's friend and author Tina Brown, left, and Princess Diana

She claimed a winter wedding would neatly avoid comparisons with the legendary February engagement and July wedding of William's parents.

And she predicts St George's Chapel at Windsor - which has hosted several royal weddings of late, including Prince Charles's marriage to Camilla Parker Bowles - is a likely venue.

William and Kate, who have been dating since meeting at St Andrews University seven years ago, have been plagued by speculation about when they will finally tie the knot.

Talk has reached fever point recently. William turns 28 this June - the age at which he once, rashly, predicted he would get married.

Even members of the prince's inner circle admit they 'haven't a clue' as he 'plays his cards so close to his chest'.

Miss Brown's suggestion seems as good as any, due to her impeccable connections with members of the British aristocracy.

Last night a St James's Palace spokesman declined to comment, saying: 'We never discuss Prince William's private life or comment on what is merely speculation.'

Sources insisted, however, that they were tempted to take the report 'with a pinch of salt'.

'Prince William has never given the merest hint about what is on his mind regarding his relationship with Kate Middleton and his office is under the clear impression that if he does decide to pop the question, they will only be told a matter of days or even hours before he wants the world to know,' said one.

'The suggestion that staff at Clarence House, St James's Palace [the official name of William's household] or even Buckingham Palace, for that matter, have been clearing their diaries, appears wide of the mark.'

Another source also suggested that William would be training at RAF Valley on Anglesey on the dates suggested by Miss Brown - which would preclude him from travelling to London to make the customary formal announcement.