Passengers at London's Stansted Airport are facing a morning of chaos after climate change protesters forced their way into a secure area, causing the complete closure of the runway.

The protest, by 54 campaigners, saw demonstrators occupying a runway and taxi area which had been closed for maintenance work at around 3am.

According to Plane Stupid, which organised the demonstration, the protest is over the Government’s decision to allow the expansion of the Essex-based airport, situated to the east of London, with a second runway.

It was set to cause chaos this morning, as all departures have so far been postponed and arrivals are expected to be diverted. Four people have been arrested.

An Essex police spokeswoman said the protesters were "airside". "We have arrested four people so far. Police have contained the area where the protesters are and they will be dealing with them in due course," she said.

BAA, operator of Stansted Airport, said the runway was closed for "safety and security reasons", and warned passengers to expect delays.

In a statement, BAA said: "At approximately 3am an unknown number of individuals breached security, but shortly afterwards were held by police. This continues to be the situation.

"Due to this event the runway is closed and will continue to be so until further notice. the advice to passengers is to contact their airlines directly who can advise them but we are expecting delays."

Explaining its reasons for the protest, Plane Stupid said aviation was the fastest growing source of emissions and already contributed to at least 13% of the UK’s carbon budget. It also pointed to plans for a new runway at Heathrow which the government has yet to approve.

One of the activists, Lily Kember, 21, said the protesters had used bolt cutters to get in to a secure area around 50 metres from the runway.

Ms Kember said a total of 54 protesters were sitting down on a site near where aeroplanes taxi before taking off and landing. "Being arrested is a terrifying prospect, but not nearly as terrifying as the threat of climate change," she said.

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