A group of 12 “climate activists” will face no penalty after staging a protest near Heathrow against airport expansion.

A number of people ran on to the M4 and A4 roads, and lay down in front of oncoming traffic, causing a temporary disruption on Saturday, November 19.

A group of 15 people, aged between 21 and 67, were charged with wilful obstruction of the highway.

At a hearing at Ealing Magistrates' Court today 12 of them pleaded guilty and were given a conditional discharge.

They were told they would each have to pay a victim surcharge and prosecution costs of £105, but a spokeswoman for the group refused to rule out a similar protest in the future.

The court heard their motivations were fears about air pollution potentially caused by a third runway at Heathrow, the urgency of climate change and social inequality.

District Judge Stephen Day gave the 12 defendants a conditional discharge, pointing out that they had pleaded guilty at the first opportunity, and that they were all of good character and had no previous convictions.

Prosecutor Richard Doolan said the protesters were joined together by plastic tubing and some of the defendants had to be cut free.

They were removed from the road in less than half an hour, he said, and the court heard that police knew a protest had been organised.

Those sentenced after pleading guilty were Madeleine Ellis-Petersen, 24, of Ealing; Joanne Louise Bodimeade, 28, of Lambeth; Alexis Delage, 25, of Lewisham; Tom Venner-Woodcock, 29, of Southwark, and Tess Lotter, 30, of Camden.

Also sentenced were Antoine Thalmann, 25, and Henry Owen, 23, both of Oxford; Simon Bramwell, 44, Gloucestershire; Ian Bray, 49, West Yorkshire; Graham Lewis, 53, of Somerset; Thomas Harford, 26, of Bristol, and Sibi Moore, 21, of Devon.

Lewis wore a white shirt in court which read "Plane crazy runway hell."

He also intervened at one point in proceedings to say he was a "trainee Buddha".

And outside the court one campaigner held a sign reading "Climate crisis is a racist crisis".

Speaking after the sentencing, Ellis-Petersen said: "It's a great result within the realms of what we were expecting."

She added: "This is not the end. We will continue to fight until the Government takes meaningful action to tackle climate change and that includes not building a third runway."

Asked if she would stage a similar protest again, she said: "If that's what it takes."

The court heard the defendants are involved in voluntary work with charities and in the community.

Owen said: "The judge recognised that we were compelled to act by the urgency to tackle climate change and sentenced accordingly.

"However, that we were in court at all fails to acknowledge that expanding Heathrow is a disastrous policy whichever way you look at it.

"It would mean more air pollution, more climate changing emissions and the bulldozing of hundreds of people's homes.

"Our protest is only the beginning of waves of action that will, in time, bring the plans to expand Heathrow to a halt."

Earlier, Isabelle Anderson, 30, of Hebden Bridge, and Sophia Lysaczanko, 28, of Haringey, pleaded not guilty to wilful obstruction.

Anderson will go on trial on February 6 at Uxbridge Magistrates' Court, and Lysaczanko will go on trial at the same court on February 7.

Margaret Charnley, 67, of Bristol, was not at the hearing as she was excused from attending but a lawyer indicated a plea of not guilty. She is also due for trial on February 7 at Uxbridge Magistrates' Court.