Called the Emirates Air Line, it soars almost 300ft above the river, offering 360-degree views of the east of the capital including the O2 concert Arena and the Canary Wharf financial district.

It opens in time for the Olympics which begin next month and will help serve three venues south of the river as well as provide a link to the Olympic Park on its north side.

Passengers can embark at North Greenwich, where the O2 concert arena is based, which will be known as the North Greenwich Arena during the Games, and where artistic and trampoline gymnastics will be held as well as some basketball games.

Nearby Greenwich Park will host equestrian events.

North of the river lies the ExCel Centre where a host of sporting events will take place including fencing, wrestling, table tennis, boxing, judo, taekwondo and weightlifting.

The Olympic Park is then a short journey away.

"I think that this will now become one of the great sights of London," said Mayor Boris Johnson. "It will be something that people want to come and see, take their children up and it's the most incredible way of viewing the city."

The 45-million-pound crossing forms part of Johnson's plans to help revive the neighbouring areas by creating jobs and stimulating growth.

"This is a developing area of London, this will help this area of London develop faster," Transport for London (TfL) Commissioner Peter Hendy told Reuters.

His comments follow criticism from Johnson's opponents, who wonder how much the taxpayer will have to contribute to the cost of the project and whether London commuters will actually use it once the Games are over.

"I think that people have got to bear in mind that the build cost of this cable car is 45 million pounds, of that 36 million pounds has been contributed by Emirates Airline, who are sponsoring it," Johnson told Reuters.

The cable cars have the capacity to carry up to 2,500 people per hour in each direction - the equivalent to 30 buses - and take five minutes to cross the river.

The stretch of Thames is currently served by road tunnels, but no bridges.

A cash single fare costs 4.30 pounds while those using London's popular "Oyster" travel cards pay 3.20 pounds.

But not everyone was convinced the service will fly.

Restaurant Manager Bobby Chan, 38, who waited 7 hours to be the first to climb aboard the cable car, told Reuters he didn't think it would be used regularly by commuters because it was too expensive.

"It's really nice, it's beautiful, it's just too pricey... It's really a tourist attraction," he said. "People who live here, a lot of people who want to cross the river, I don't believe that they're going to really use it.

"It's just too much. You're better off just using the trains, it's a lot cheaper." (Additional Reporting by Will Russell; Editing by Ossian Shine)

• A Permanent Economic Emergency