The Olympic flame arrived in Britain from Greece on Friday to start a 70-day relay which will culminate in the opening ceremony of the London Games.
Princess Anne, the daughter of Queen Elizabeth II, accompanied by football star David Beckham, carried the flame down the steps of a special British Airways jet at Royal Naval Air Station Culdrose in Cornwall, southwest England.
"It comes home to you just how important people regard the torch (relay) as the lead-up to the Games," said the princess, who herself competed in the 1976 Olympics in an equestrian event.
Beckham had the honour of lighting the torch that will be used for the 8,000-mile (12,875-kilometre) relay, from a cauldron at the airbase, as hundreds of spectators cheered.
Sailor Ben Ainslie, who has won gold in three Olympics, will be the first of some 8,000 torchbearers when the relay starts in Land's End, the southwesterly tip of England, shortly after 0600 GMT on Saturday.
The flame was handed over to the British delegation in a ceremony in Athens on Thursday and was transported from the Greek capital in a passenger jet painted gold and renamed The Firefly for the occasion.
Organisers gained special permission from aviation authorities for the flame to be carried in the plane encased in a special lantern.
The weather in the Greek capital had been decidedly British, with heavy rain, but it was dry and breezy in Cornwall when the plane touched down.
Chief organiser Sebastian Coe, who also went to Greece for the handover of the flame, said its arrival was "a magical moment for any host country".
"It will connect millions of people around the UK to the Games in a unique way and allows us to celebrate the best of the UK and its people," he said.
The torch will visit more than 1,000 cities, towns and villages on its journey to the Olympic Stadium in east London, as Britain hosts the Games for the first time since 1948.
Deputy Prime Minister Nick Clegg, who was at the airbase to greet the flame, said: "Eight thousand people will pass it from hand-to-hand, a human chain that reaches the length and breadth of Britain. With every step, the excitement will build."
From June 3-7, it will visit Northern Ireland and then the Republic of Ireland -- the only country outside the United Kingdom on the torch route.
The inclusion of the Republic would have been unthinkable just a few years ago and shows the ever-closer ties between it and Northern Ireland, 14 years after a peace agreement largely ended three decades of sectarian strife in the north.
In mainland Britain, a soldier wounded in Afghanistan and a 100-year-old woman will be among the torchbearers, organisers have said.
Also set to carry the flame is Jim Redmond, the father of former British 400 metres runner Derek Redmond, who famously helped his injured son hobble across the line during the 1992 Barcelona Olympics.
The torch relay culminates on July 27 with the final leg from Hampton Court Palace, the riverside former home of king Henry VIII, to the Olympic Stadium for the opening ceremony.
The torch is a reminder of the ancient Olympics, when a flame burned throughout the Games. The tradition was revived in 1936 for the Olympics in Berlin, when the Nazis used it for their own nationalistic purposes.
No overseas legs of the torch relay have been planned this year after those before the 2008 Beijing Games were hit by widespread protests against China.