Terry Maher, 44, climbed on top of a tunnel above the railway line outside London's St Pancras terminal on March 29, the day Britain was originally due to leave the European Union.

He spent 13 hours overnight on the tunnel, carrying an English flag, power banks for his phone and warm clothing.

Some 88 trains including Eurostar were cancelled and around 22,000 people were directly affected, delayed, inconvenienced or had to abandon their travel plans.

The high-speed train line links London with Paris and Brussels. International passengers were left stranded overnight.

The disruption is estimated to have cost more than £1 million ($1.2 million, 1.1 million euros).

Maher, who lives near St Pancras station, was found guilty of malicious obstruction of the railway and was sentenced to one year in jail at Blackfriars Crown Court in London on Monday, the British Transport Police said.

"Not only did it cost the rail industry, it also cost thousands of commuters and holiday-makers their time, significantly delaying their journeys and leaving them stranded at stations desperate for the situation to be resolved," said investigating officer Detective Sergeant Dean Percival.

"Maher's selfish actions profoundly impacted the day to day lives of the public; that impact is what he was brought to court to answer for."