Witnesses have described horrifying scenes of train passengers trampling over each other to escape a mass stabbing in the UK.

A 32-year British national is now the only suspect for the stabbing on a London-bound train, which police are not treating as a terror attack. 

One of the 11 victims - described by police as a hero who tried to intervene - remains in a critical condition.

UK correspondent Gavin Grey says the driver also moved quickly to get the train the in the right lane so police could intervene. 

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