London, Apr 21: Queen Elizabeth, her fortunes revived after a turbulent decade for the royal family, turned 80 today with her eyes perhaps set on becoming Britain's longest-reigning monarch.
With a decade to go before she would rival Queen Victoria's 64 years on the throne, this working grandmother shows no signs of slowing down and seems to have genes on her side, her mother died at 101.
Crowned nearly 53 years ago, she firmly rules out abdication and opinion polls suggest republicans face a losing battle calling for the abolition of the monarchy while she is still alive.
In an ITV News survey, she was rated the most popular royal.
Bottom of the pack came Camilla, Duchess of Cornwall, who last year married the queen's eldest son Charles after a tortuous 35-year romance.
At their wedding reception, the queen told her guests: ''My son is home and dry with the woman he loves.'' Her subjects are less impressed, with more than half those polled feeling Camilla should not become Queen when Charles finally accedes.
Britain's most famous octogenarian has opted for a strikingly low-key day of celebrations to mark her personal milestone.
She will be spending the day at Windsor Castle, ravaged by fire in 1992, the year she memorably called her ''annus horribilis'' after the marriages of three of her four children broke up.
Stepping out of the castle, she will head off on a walkabout among her subjects -- a tradition she first adopted in a tour of Australia and New Zealand in 1970.
Then Charles is to host a private family dinner for his mother.
The two are much closer now that his tangled love life has finally been sorted out.
His first wife Princess Diana, killed in a Paris car crash in 1997 that provoked an outpouring of grief from Britons, had always blamed Camilla for the breakup for her marriage to Charles.
The queen, born in 1926, suffered a backlash from her children's disastrous marriages but now public opinion is broadly pro-monarchy, at least until she dies.
Veteran Mail on Sunday columnist William Rees-Mogg said, ''We have been living through a great reign comparable in length but also in achievement with the reigns of her predecessors, Queen Elizabeth I and Queen Victoria.'' Daily Mirror royal correspondent James Whitaker begged to differ, telling Reuters: ''I really, really admire her but I don't think she will go down in history as a great sovereign.'' He added, ''Three of her children got divorced. That is a hell of a fallout in one family by any standards.
''Everything is fine for the monarchy while she is alive. I am not sure it is fine when she is dead. I don't think we want Charles to come to the throne in any real hurry.''