Thirteen anti-Heathrow expansion activists have gone on trial for occupying the airport's northern runway in July.

JULY: Heathrow protesters removed from runway

They have all pleaded not guilty at Willesden Magistrates' Court to aggravated trespass and being unlawfully airside without authority.

Defence witnesses to be called include Hayes and Harlington MP John McDonnell, as well as Green Party Mayoral candidate Sian Berry.

A demonstration in support of the activists took place outside the court this morning, organised by campaign group Reclaim the Power.

Plane Stupid spokesman Sam Jones said: "Plane Stupid took action last July to stop emissions from aircraft.

"Aviation is the fastest growing source of carbon emissions and Heathrow is the biggest airport in the Europe by a long way.

"Building a third runway would cross a red line that would jeopardise our ability to combat climate change.

"This isn't about people taking business trips, or their annual holidays, this is about the minority of frequent leisure fliers who take trips to their second homes, weekend breaks and tax havens – that 15 per cent of the UK population takes 70 per cent of the UK’s flights.

"David Cameron famously asserted in 2010 that Heathrow would not be expanded, "no ifs, no buts".

"The fact that the government is now U-turning spectacularly on this promise demonstrates why you can't leave this sort of thing to politicians.

"Plane Stupid has been taking action against airport expansion for nearly a decade, and we aren’t going anywhere - we are in it for the long haul."

The trial is expected to last two weeks with the verdict to be delivered at Uxbridge Magistrates' Court on January 29.