The decision by British Prime Minister David Cameron to remove Justine Greening from the cabinet post of transport secretary has airbrushed out a key political obstacle to a third runway at London Heathrow airport.

Conservative Party member Greening represents the southwest London constituency of Putney, Roehampton and Southfields – which lies directly beneath Heathrow’s flightpath.

She was re-elected to parliament by local residents on an anti-third runway ticket in May 2010, subsequently being appointed to the post of transport secretary by Cameron in October 2011.

Greening’s opposition to Heathrow expansion lent credibility to pledges made in 2010 by the incoming Conservative-Liberal Democrats coalition government that a third runway will not be built at the west London site.

But in recent months business groups and aviation lobbyists have won over a growing number of Conservative backbenchers, who now believe the UK economy is being damaged by constrained airport capacity.

Though Greening's departure marks a shift in tone, any wholesale reversal of the government’s policy would require delicate political manoeuvring.

During the 2010 general election – in which the Conservatives failed to win an absolute majority – Cameron had sought to boost his party’s environmental credentials by unequivocally promising: “No ifs, no buts, no third runway.”

The prime minister has since softened his stance, stating in March: “I’m not blind to the need to increase airport capacity, particularly in the southeast.”

Greening, meanwhile, steadfastly refused to reconsider her position, insisting as recently as last week that the third runway is “not a long-term solution” and intimating that she would step down if the project was resurrected.

Coalition partners the Liberal Democrats also remain broadly opposed to Heathrow expansion.

An alternative proposal to develop a new hub on the Thames Estuary east of London still enjoys the backing of London Mayor Boris Johnson, but the project has failed to gain traction elsewhere due to its uncertain cost and timeframe.

Greening is succeeded as transport secretary by Patrick McLoughlin, member of parliament for Derbyshire Dales.

Source: Air Transport Intelligence news