Heather Mills-McCartney joined some of Britain's most successful women for a power lunch with the Queen.

The former model, married to ex-Beatle Sir Paul McCartney, mingled with more than 180 high-flyers including author JK Rowling, singer Charlotte Church and former prime minister Baroness Thatcher at the all-female event at Buckingham Palace.

Lady Mills-McCartney, who gave birth to daughter Beatrice four months ago, revealed the woman she was most pleased to meet was Baroness Thatcher.

She told her how she had once chatted to her late husband Sir Denis about living with a powerful politician.

The anti-landmine campaigner, who has homes in Hove and Peasmarsh, near Rye, said: "I asked him how he coped and what it was like to be with such a strong woman.

"He told me, 'She might be the boss in the boardroom but I'm the boss in the bedroom'."

Lady Mills-McCartney also chatted to the Queen at yesterday's event, organised to pay tribute to women from all walks of life, including academics, actresses and sports stars.

They were joined by the Princess Royal, the Countess of Wessex and the Duchess of Gloucester.

Other guests to make the journey from Sussex included the actress Dame Joan Plowright, who lived with her late husband Lord Olivier in Royal Crescent, Brighton, before moving to Ashurst, near Henfield.

The Countess of Wessex was spotted chatting to Tiffany heiress and charity activist Rosa Monckton, who lives in East Sussex and was one of the closest friends of Diana, Princess of Wales.

The Countess was taking part in her first official engagement since the birth of her daughter Lady Louise and was said to have made an exception to her break from royal duties because she was particularly interested in the event.

Also on the guest list was Sam Taylor-Wood, whose Self-Portrait In A Single-Breasted Suit With Hare was exhibited at Brighton Museum and Art Gallery last October.

The artist chatted to charity campaigner Jemima Khan and supermodel Kate Moss, who wore a royal blue dress matching the Queen's outfit.

Also representing the fashion world was Alexandra Shulman, who studied social anthropology at Sussex University before working for Tatler magazine and becoming editor of GQ and Vogue.

Historian Lady Antonia Fraser, wife of playwright Harold Pinter and daughter of Lord and Lady Longford, whose family had an estate near Robertsbridge, was also invited.

Guests dined on casserole of salmon and monkfish, sauteed loin of lamb, risotto of mushrooms and courgettes, followed by passion fruit cheesecake for dessert.

Lady Mills-McCartney would have approved of the musical selections, which included a "best of The Beatles" performed by the Welsh Guards band as well as more classical offerings.

Dame Shirley Bassey said the day was long overdue.

She said: "I'm glad Her Majesty has done this. Men have had it their own way for too long."