Arsene Wenger also revealed record signing Mesut Ozil, who had looked refreshed and scored in the 4-1 FA Cup quarter-final win over Everton on Saturday, could be set for a lengthy spell on the sidelines:
We have to make a scan tomorrow to see how bad it is but he's out for at least a few weeks. I hope it's not too bad.
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One professor warns of a 'potentially disastrous capacity crunch'.
A number of families were on board the service from London Euston to Stoke. One family left the train early to escape the abuse.
She's called Amy, and was visiting a hospital.