They were the most committed climate change activists in Britain, they had trained in the arts of direct action protest and were determined to disrupt the workings of the British Airports Authority. All that stood in their way was nearly 2,000 police officers.

Leaving their camp outside Heathrow airport yesterday afternoon, the protesters declared that they were armed “only with peer review science”.

The police were armed with riot gear and supported by mounted units, vans, squad cars and a helicopter. If this was a David and Goliath battle, then last night Goliath appeared to be winning.

“Whilst the car park to one of our office buildings currently has a number of protesters in it, BAA’s operations have not been impacted in any way,” a spokesman for the company said.

There had, however, been skirmishes along the way. Protesters complained of heavy-handed treatment: some were knocked to the ground by riot police, while police complained that protesters had hurled missiles as they advanced through a field behind the BAA headquarters – one mounted officer was knocked from his horse.

The first divisions of the army of climate change activists left the camp shortly after noon, singing of the perils of aviation and global warming.

They were diverted to the north, and corralled at the side of a road by scores of police officers. Some tried to break out, there was a scrimmage as the police bunched together and forced them back.

Ben McKinnon, 28, from Suffolk, said: “We were being held illegally. I tried to go between two officers. They held me down, I think I was being kicked. I fainted.” He was treated by a police medical officer.

A handful of local residents arrived to support the marchers. Danny Shaw, 50, a shopfitter from West Drayton said: “This is crazy, it’s a peaceful protest, there are far too many police. It’s bullying tactics.” Shortly afterwards the protesters were released, to band up with a following group of several hundred activists carrying decorated parasols, rainbow flags, anarco-syndicalist flags and antiaviation banners. At the lead were local children.

“I don’t want my house to be knocked down,” said Olivia Howard, 8, from the village of Sipson, which would be demolished to make way for a proposed third runway and sixth terminal.

Back at the camp, smaller “affinity groups” of protesters were leaving in all directions. Several hundred leapt the fence behind the camp and headed through the fields behind the BAA headquarters. A dozen riot police vans were diverted down narrow lanes between the fields in an attempt to head them off.

John Ackers, a software developer from North London, who was one of a small band that called itself the Outlaws, said: “We played a game of cat and mouse for a while in the fields, we kept changing directions and finally broke through. The police had truncheons out and they were hitting people. Every time we came to a fence they would form a line and start hitting.”

Some made it through the lines and headed via a maze of residential streets towards the back of the BAA building, only to be cut off again by ranks of riot police. On the corner of a perimeter road that skirts the north side of the airport, five protesters were knocked to the ground in the forecourt of a petrol station. “Medic! Medic!” shouted one of the officers.

By 4pm several hundred protesters had managed to take up residence in one of the BAA car parks. Three had scaled a scaffold opposite and unfurled a banner that read “Make planes history”.

A group of drama students dressed as monks, calling themselves the Curious Theatre Collective, organised a mock service “in praise of BAA.” Opposite, a man was restrained while attempting to glue himself to a car. He was arrested, one of six arrests that had been made by 8pm yesterday. The police had previously arrested 41 protesters in the course of the camp.

A spokesman for BAA remained confident that operations would continue as normal. Protesters said they would lay siege to the site throughout the night. Some set up tents in the car park. One of them, John, 38, from Blackpool, told The Times: “We will let staff get out but we will try to prevent any getting in and we will try to stay here as long as possible.”

Airport under siege

47: People arrested over the protests by last night

2,000: People estimated to have taken part in protests this week

1,800: Officers deployed in response

79m: Passengers handled in Heathrow a year

15%: Increase in first-time private jet bookings this week

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