The campaign group Plane Stupid said three of its members parked the van across the tunnel at 7.40am and unfurled a banner quoting David Cameron’s election promise: “No ifs, no buts: no third runway.”
The Metropolitan police said they were called to the scene soon after, and by 8.40am officers had made five arrests for “obstruction-related offences”. The force said the protesters were removed and the road reopened by about 11.10am.
A video posted to Twitter showed a small white van parked across both lanes of the carriageway inside the tunnel, with traffic backed up behind it. Motorists held up by the protest had got out of their vehicles but appeared calm.
On the side of the parked van there was a banner that said “No new runways”. In the video, a protester is lying next to the front left wheel of the vehicle, presumably locked to it.
The demonstration blocked the inbound section of the tunnel. A contraflow system was put in place on the outbound section in an effort to clear the traffic.
Cameron Kaye, a spokesman for Plane Stupid, said the protest was being staged to draw attention to concerns about the impact a third runway could have on the environment.
“Airport expansion would wreck the legally binding Climate Change Act, risking wiping out 55% of species this century and displacing 75 million more people from their homes by 2035,” Kaye said in a statement on the group’s website.
“If aviation growth isn’t reduced, by 2037 aviation alone could emit all of the carbon it’s safe for the UK to emit. The government needs to choose: build new runways or stop climate chaos. It’s that simple.”
A spokesman for Heathrow said passengers planning to travel to the airport by road should set off earlier.
“We can confirm there is a protest taking place in the inbound tunnel which is currently affecting traffic around the central terminal area and Terminals 2 and 3 at Heathrow,” the spokesman said. “Police are now on site but we urge passengers to allow extra time getting to the airport today.”