Britain finally approved a new 16 billion pounds ($33 billion) underground rail link across London designed to carry 200 million passengers a year and ease the capital's clogged transport network.
The government on Friday hailed Crossrail as Europe's biggest civil engineering project and said it should be running by 2017.
"By generating an additional 30,000 jobs and helping London retain its position as the world's pre-eminent financial centre, it will support Britain's economic growth," Prime Minister Gordon Brown said.
The plan to connect the western and eastern ends of London via a tunnel was first proposed in the 1980s but has produced little more than planning meetings and parliamentary debate.
Businesses feared that London would slowly lose its status as an financial hub unless it fixed its transport problems.
The project will add 10% more capacity to the underground rail network, improve the business districts' links to Heathrow airport and support the urban regeneration expected around the site of the 2012 Olympics.
It had been deadlocked for weeks over 350 million pounds of missing funding, which the authority governing London's financial district agreed to pay at an emergency meeting on Tuesday.
The City Corporation also helped fund London's original underground railway in the 1860s.
"It is the key to the next 20 years of economic development of London," said London mayor Ken Livingstone who estimates the rail link could benefit the London and southeast economy by more than 30 billion pounds.
The announcement came as Brown agonizes over whether to call a snap general election this week.
Speculation has been running high that the new prime minister would seek his own mandate by calling an election for Nov. 1.
"Getting the go ahead for Crossrail has been like piecing together a giant jigsaw, but with real UK jobs and GDP growth at stake," said Baroness Jo Valentine, chief executive of London First, which represents over 300 London businesses.
"Canary Wharf, BAA and City of London have all made important contributions," she added.
Crossrail will be one of Britain's biggest-ever building projects, exceeding the 7.5 billion pounds spent on digging the Channel Tunnel and the 9.3 billion pounds budgeted for the 2012 Olympics.
In central London, the trains will run through deep tunnels, with stations at Paddington, Bond Street, Tottenham Court Road, Farringdon, Liverpool Street and Whitechapel.
It will increase the rail capacity serving Canary Wharf by 54% and by 21% in the City financial district.
"Crucially for London's future, when Chinese and Indian businesses consider where to site their European headquarters, they will see in London a world city investing in its future," said Valentine.