Three environmental activists who blocked a tunnel at Heathrow airport last year have been issued fines of £200 each by a court on Tuesday.

The protest by Plane Stupid activists last November was part of a series of actions by the group against the expansion of the airport, including the so-called Heathrow 13 who in February were spared prison sentences for occupying the airport’s runway.

Members of the Heathrow 13 were among 30 campaigners outside Uxbridge Magistrates Court, as a judge sentenced Esme Waldron, Alistair Cannell, and William Pettifer to pay £200 each plus prosecution fees for wilful obstruction of a public highway.

The trio had originally pleaded not guilty to the charge after parking their van across the road in the tunnel, causing disruption for around three hours, but later changed their plea to guilty. The fines were reduced from £300 to £200 because of the plea change.

Waldron said: “For most of us, all we will gain from new runways is dirtier air, more noise and more floods due to climate chaos. There are more than enough runways for people who take one holiday a year; demand for airport expansion only comes from a minority of frequent leisure flyers.”

A spokesman for the airport said: “Heathrow supports the right to peaceful protest, but we will always prioritise the safe and smooth running of our airport. When individuals engage in illegal protest action, they disrupt thousands of passengers going about their business and pose a safety risk to themselves and others.

“Anyone who breaks the law, puts safety at risk and disrupts our passengers and colleagues will face prosecution.”