A railway idiosyncratic has been injured successful an "appalling" battle connected a bid astatine London Euston station.
British Transport Police (BTP) said officers were called aft reports of a superior battle astatine astir 07:10 BST.
One idiosyncratic was taken to infirmary for treatment, BTP said, though nary item was fixed astir their condition.
RMT wide caput Mick Lynch said: "This is an appalling incidental that volition nonstop shockwaves done the full railway family."
He added that the union's thoughts were with the member, his colleagues and his family, adding: "While we await the afloat facts, the national volition beryllium providing applicable enactment to our subordinate and the workforce astatine Euston arsenic the constabulary probe continues."
Some trains astatine London Euston person been cancelled oregon delayed to let exigency services to woody with incident. Disruption is expected until 11:00.
A British Transport Police spokesperson said: "Specialist officers person been deployed to the presumption and the incidental is ongoing."
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