Queen Elizabeth, who celebrated the 70th anniversary of her accession to the British throne over the weekend, will be returning to normal duties, a Buckingham Palace source said on Monday, having been advised to take it easy by her doctors.

The 95-year-old, the world's oldest and longest-reigning monarch, has been little seen in public since she spent a night in hospital last October for an unspecified ailment, and was then instructed by her medical team to rest.

On Sunday, she became the first British sovereign to spend seven decades on the throne in a dynasty that traces its origins back almost 1,000 years to Norman King William I and his 1066 conquest of England.

Buckingham Palace said the queen, who spent the occasion at her Sandringham residence in east England, had now returned to her Windsor Castle home where she will resume her official duties.

Despite her advancing years and the loss of her husband Prince Philip last year, she has continued to perform high-profile engagements, and a palace source said she would now resume her routine of audiences and meetings, both in person and virtually.

She is expected to attend three engagements in person in March: a diplomatic reception at Windsor Castle, the Commonwealth Service at London's Westminster Abbey, and a service of thanksgiving at the same venue for the life of Philip, her husband of 73 years who died aged 99 last April.

"I was blessed that in Prince Philip I had a partner willing to carry out the role of consort and unselfishly make the sacrifices that go with it. It is a role I saw my own mother perform during my father's reign," Elizabeth said in a message to the nation to mark her 70th anniversary of becoming queen.

"I remain eternally grateful for, and humbled by, the loyalty and affection that you continue to give me."

Elizabeth also chose the occasion to give her blessing to Camilla, the second wife of son and heir Prince Charles, becoming Queen Consort when he succeeds her.