Eurostar have suspended all services to and from St Pancras this morning due to a suspected Brexit protester.
A man has been pictured waving a St George's Flag above lines near the central London station.
Police negotiators working overnight have been unable to talk him down without success and disruption is expected until at least midday.
Passengers have been advised not to travel on Eurostar at all this morning and thousands of passengers in the UK and in Europe have been affected.
The disruption was first reported to British Transport Police at 7pm yesterday.
The 'protester' is also causing ongoing issues on Southeastern.
Have you been affected by the disruption? Email webnews@mirror.co.uk
Sky presenter caught saying ‘b*****ks on-air during heated Brexit discussion
Southeastern said on Twitter: "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."
Passengers on Southeastern have been advised to travel to Victoria or Charing Cross stations rather than St Pancras.
A spokesman for National Rail said: "The trespasser just outside London St Pancras International is still on the railway viaduct that crosses the high speed lines just outside the station.
"Police negotiators have been on site over night trying to talk the trespasser down but as yet have been unable to. Unfortunately due to the overhead wires below the person, which have been isolated, Eurostar and High Speed trains to London St Pancras International are unable to run."
DUP would rather REMAIN in the EU than risk Northern Ireland's place in the UK
Eurostar said: "We have suspended all services to and from London St Pancras this morning, due to a trespasser on the tracks.
"We strongly recommend you not travel this morning and please cancel your journey or exchange ticket free of charge for a different date."
One Eurostar user tweeted: "Trying to take the Eurostar from Paris to the UK, but all trains have been suspended. Stuck in France."
Vote Leave drops appeal against EU referendum spending fine - on Brexit Day
Shortly after 10pm yesterday British Transport Police tweeted: "Just after 7pm officers were called to a man in a precarious position at St Pancras. They, along with colleagues from other emergency services, are working to resolve the situation as soon as possible.
"Thank you to everyone whose journeys have been disrupted for your patience."
A Eurostar spokeswoman said the trespasser was located near St Pancras station.
Southeastern said that the overhead wires are not able to be recharged while the "person is above the high speed lines".
The statement said: "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."
Thousands of Leave supporters gathered outside Westminster on Friday afternoon as Theresa May’s third attempt to secure a deal was rejected by MPs.
The Met Police said they made five arrests, including one man on suspicion of assaulting a police officer.
