Officers were called just after 7pm on Friday – the day of the “Brexit Betrayal” march – after the man was seen “in a precarious position” over the high-speed lines.
Photos of the scene showed the trespasser carrying a St George’s flag on a roof above the tracks, leading to speculation it was a pro-Brexit protester.
Eurostar announced that all services to and from St Pancras would be suspended until 9.45am.
Opposing protesters flock to parliament on would be date of Brexit
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Southeastern trains were also disrupted. The company announced: “High speed trains will not run to and from St Pancras due to the ongoing trespass incident just outside the station.
“The person is above the high-speed lines and as such the overhead wires can not be recharged.”
Shortly after the man was arrested, Eurostar said its services would resume soon but advised passengers not to travel on Saturday morning and either cancel their trip or exchange their ticket. Eurostar trains were already disrupted due to industrial action by French customs officials in Paris until 3 April.
The British Transport Police said in a statement: “Just after 7pm last night (Friday 29 March 2019), British Transport Police officers, along with other emergency services, were called to a man on the roof of St Pancras Railway Station.
“This morning (Saturday 30 March) a 44-year-old man has been arrested for trespass and obstruction of the railway. Passengers should contact rail operators for current information on their train journeys. We thank everyone for their patience.”
National Rail said the disruption to train services would continue until 11am.
On Friday, thousands of pro-Brexit supporters gathered in central London on the day the UK was supposed to leave the EU.
Former Ukip leader Nigel Farage and Tory Brexiteer MP Mark Francois spoke at the ”March to Leave” rally in Parliament Square while Ukip leader Gerard Batten and English Defence League founder Tommy Robinson made speeches at a separate “Make Brexit Happen” rally near Whitehall.
The Metropolitan Police said five people were arrested, including two for assault, one for drunk and disorderly, one for assaulting a police officer and one who was identified as wanted for an offence in Hertfordshire. “All are now in custody,” the force said.
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