Queen Elizabeth II is preparing to celebrate her 90th birthday on Friday with a family gathering as a new poll finds Britain’s longest-serving monarch is as popular as ever.

The Queen has reigned for more than 63 years and shows no sign of retiring, even if she has in recent years passed on some of her duties to the younger royals.

A new poll suggests the British public want it to stay that way, with 70 per cent saying she should reign for as long as possible, the highest proportion since 1981.

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Support for the monarchy remains high at 76 per cent, according to the Ipsos-Mori poll for King’s College London.

“The Queen is hugely popular, she is liked personally and is felt to have done an excellent job,” Roger Mortimore, a professor at the Institute of Contemporary British History at King’s College London, said.

The celebrations will be low-key, with the main public events, including a military parade and lunch for 10,000 guests on The Mall outside Buckingham Palace, taking place as part of her official birthday celebrations in June.

With her husband, Prince Philip, she will meet members of the public near Windsor Castle, her weekend residence, before lighting the first of a chain of beacons stretching across Britain and its overseas territories.

At an event in Windsor’s town hall, the Queen will be presented with a cake baked by Nadiya Jamir Hussain, the winner of the Great British Bake Off, a hugely popular television cooking competition.

The Muslim mother-of-three will present the orange drizzle cake, with orange curd and orange butter cream, to the Queen personally, a prospect she said has left her “so nervous I can’t even look at the oven”.

The Queen will also attend a family birthday dinner organised by her heir Prince Charles, emphasising her role as the head of four generations of the House of Windsor.

Charles and his son William are increasingly taking over the Queen’s duties, although she still carried out 393 engagements last year, including state visits to Malta and Germany.

William, who with his wife Kate and two young children has brought fresh energy to the royals, paid tribute to the matriarch he and his brother Harry describe as “the boss”.

“I am incredibly lucky to have my grandmother in my life. As she turns 90, she is a remarkably energetic and dedicated guiding force for her family,” William said.

Impartial Queen a respected ‘constant and stabilising presence’

The Queen has seen 12 prime ministers pass through Downing Street since she ascended to the throne in 1952, meeting them once a week at the palace and still receiving daily updates of the workings of parliament.

Conservative Prime Minister David Cameron will pay tribute to the monarch in parliament on Thursday (local time), while US President Barack Obama will join the Queen for lunch at Windsor on Friday (local time).

The Queen is widely viewed as a constant and stabilising presence in a turbulent world, a status she has cultivated by refusing to make public her personal views.

In September last year, she broke Queen Victoria’s record to become Britain’s longest-reigning monarch, but played down the achievement, saying it was “not one to which I have ever aspired”.

“Inevitably, a long life can pass by many milestones. My own is no exception,” she said.