The British government has finally given the go-ahead to a third runway for London's Heathrow airport - hailed as evidence a post-Brexit Britain is "open for business".

Coming after decades of indecision, it's hoped the new 22-billion-dollar runway will maintain Heathrow's place as Europe's leading airport hub. 

Outside the British Parliament protesters rail against the government's decision. A third runway, they say, will be catastrophic, adding to noise and air pollution levels already above legal limits. 

"We know that aviation is the fastest growing source of greenhouse gas emissions, we know that this massive expansion as well as having lots of local environmental impacts will certainly have global environmental impacts as well." Green Party MP Caroline Lucas said.

The decision on Heathrow comes after years of discussion and a $30 million dollar public inquiry. Gatwick Airport was the main challenger for additional runway space but lost out to the much richer and busier Heathrow. Britain's Transport Minister said it was an important post-Brexit moment.

"This is a really big decision for this country. But it's also the clearest sign post-referendum that this country is very clearly open for business." UK Transport Secretary Chris Grayling said.

For others in government, though, the price is too high.
 
"Building the third runway slap bang in the middle of the Western suburb in the greatest city on earth is not the right thing to do. No other world city would dream of subjecting so many 100's of thousands of people to more noise pollution in the way that the third runway would." UK Foreign Secrectary Boris Johnson said.

So, after what some in Britain are calling four decades of dithering, Heathrow Airport has finally got the answer it was looking for.

That, though, could be far from the end of it Anticipate another 10 years of public protest; legal challenge and Parliamentary scrutiny. Some say, it'll be lucky if this project ever gets off the ground.