According to The Telegraph, witnesses said there was a "stampede" for the cloakroom after Jessie J finished performing at 11.40pm.
A dispute broke out and a man was stabbed in the neck with a broken bottle.
They reported seeing a "huge" amount of blood.
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Housing, Communities and Local Government Secretary Robert Jenrick is hosting Sunday's coronavirus briefing.
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Tobias Weller, who has cerebral palsy, has raised more than £46,000 for Sheffield Children’s Hospital and Paces School.