Conspiracy theorists in London are speculating that Cherie Blair, wife of former PM Tony, arranged to be out of the country today to avoid having to attend a Downing Street luncheon with the Queen.

The wives of the present PM David Cameron (Sam) as well as those of Gordon Brown (sarah) and Sir John Major (Norma) are all at the diamond Jubilee lunch.

Baroness Thatcher, who rarely goes out in public anymore, is not attending.

Cherie Blair and the Queen have a long and difficult history.

Alistair Campbell, Blair's spin doctor, wrote in his diaries that the Queen’s chilliness towards Mrs Blair dated from her first Balmoral visit.

Mr Campbell said: “Cherie said she had asked the Queen if the John Brown story of Queen Victoria having an affair with her ghillie was true. She said it got a bit frosty after that.”

A book by Paul Scott published in 2006 claimed that Mrs Blair's rift with the royals started when she met Princess Anne in 1997.

The Prime Minister's wife suggested she call her 'Cherie', the book claims, but Princess Anne allegedly replied: "Actually, let's not go that way. Let's stick to Mrs Blair, shall we?"

The late Queen Mother was said to be ' mortified' when Mrs Blair wore trousers to lunch on her first visit to Balmoral, and although Mrs Blair reluctantly agreed to curtsey in public, she refused to do so in private.

A spokesman for Mr Blair told the Telegraph today: "Mrs Blair had hoped to go but she is working on a legal case out of the country so is unable to attend."