London Olympics final countdown begins

The Olympic flame is heading along the Thames on the Queen's rowbarge Gloriana on the final day of the torch relay.

A mass bell-ringing took place for three minutes from 08:12 BST (07:12 GMT) to mark the Cultural Olympiad. Big Ben chimed 40 times during the period.

It was the first time since the funeral of King George VI that the famous bell had rung non-stop for three minutes.

Organisers have released a video clip giving a sneak preview of Oscar winner Danny Boyle's opening ceremony, featuring groups in colourful stage outfits dancing to Tiger Feet by 1970s rock group Mud and cyclists with wings pedalling along to Come Together by the Beatles.

In other developments:

London taxi drivers who were to protest at Hyde Park Corner over their ban from using Olympic traffic lanes have been banned by the Metropolitan Police.

About 60,000 people gathered in Hyde Park on Thursday night to see the final torchbearer light a cauldron in front of 60,000 people as London Mayor Boris Johnson wished the crowds a wonderful Olympics, and thanked them for their support

The mayor of London has hit out at US presidential candidate Mitt Romney for comments suggesting Britain is not ready to stage the Olympic Games

Europe's largest bell will ring inside the Olympic stadium at 21:00 BST at the start of the £27m extravaganza, featuring a cast of 10,000 volunteers and said to be a quirky take on British life.

Some 15,000 square metres of staging and 12,956 props will be used, and the event will boast a million-watt PA system using more than 500 speakers.

The crowd of about 80,000 will include the Queen and a host of dignitaries and celebrities.

As late as Thursday night, Games organisers said that the ceremony had not sold out and tickets in the two highest price categories, costing £2,012 and £1,600 were still available.

Earlier, the torch relay is at Hampton Court Palace, where it wove through the famous maze before travelling down the Thames.

The final torchbearer of the 70-day relay will be 22-year-old basketball player Amber Charles, who played a key role in London's winning bid and who will carry the flame in front of City Hall and Tower Bridge at approximately 12:45 BST.

The relay ends late in the evening with the lighting of the cauldron during the opening ceremony but the identity of the person who will take on the honour remains a mystery.

The chief executive of the Olympic Delivery Authority, Dennis Hone, said he was thrilled the big day was finally here.

He told BBC Radio 5 live: "When you look around at the park, you look at the venues, the 100 hectares of landscaping, the 2,000 trees, all the plants in bloom, it's looking fantastic. It's going to be a great day, it's going to be a great 17 days of sport."

The Mayor of London, Boris Johnson, told the programme: "What's so amazing is just the wave of excitement seems to pass from person to person like some benign form of contagion. Everybody is getting it."

The Queen and Prince Philip will host a Buckingham Palace reception for heads of state and government and an opening ceremony celebration concert featuring Snow Patrol, Stereophonics, Duran Duran and Paolo Nutini will be held in Hyde Park.

And the sporting action, which officially began on Wednesday with the women's football competition, continues with archery at Lord's cricket ground.

More than 10,000 athletes from 204 nations will take part in the London Olympics.

Some £9bn of public money has been spent on staging the Games but PM David Cameron, who toured the Olympic Park on Thursday, has stressed the opportunity presented by the Games at a time of economic fragility.

"Let's put our best foot forward, we're an amazing country with fantastic things to offer. This is a great moment for us, let's seize it," he said.