The Brexit protester who disrupted services on the Eurostar last week by standing on top of St Pancras station in London has admitted a charge at Westminster magistrates court of causing a public nuisance.

Terry Maher, 44, from Camden, north London, climbed on to the roof of the station at 7pm on Friday and remained there until 8am on Saturday. He waved a St George’s flag and told arresting officers he was angry at politicians for “fucking up Brexit”.

Maher’s actions took place on the day the UK was supposed to leave the European Union and caused the cancellation of eight Eurostar services and major delays for thousands of passengers.

Southeastern also cancelled 16 services on the high-speed rail line, and delayed many more.

Robert Simpson, prosecuting, said: “The defendant managed to gain access to the roof of the building and he told the police at the time he had a Stanley knife.

“There was a total of 1,757 minutes of lost time as a result and the estimation is that there will be in excess of £40,000 in delay fines.”

The disruption caused delays for 7,000 to 8,000 passengers, Simpson said.

Maher told police he had “thought he was going to need bolt-cutters” to get on to the building and went on to say he disliked politicians, saying they were “fucking up Brexit”. He also made comments about migrants in the country and complained about foreign aid money spent in India.

Maher, who was remanded in custody, will appear at Blackfriars crown court on 29 April over a second count under the Malicious Damage Act.

The district judge, Richard Blake, said the protest was “very serious indeed” and warned others against similar action. “I hope a wider audience at large reflects on the gravity of these offences before they might be encouraged to follow your behaviour,” he said.

He told Maher: “People must understand that even when issues of great national concern are in the public domain, and we live in a free society where they can express their views, that if they resort to manners of protest which cause widespread public disruption, which you did, I should think untold members of the public had their weekends spoiled.

“It cost many thousands of pounds.”