- Ella is described as white, 5ft 7ins tall
- She was wearing blue jeans, a green coat and a jumper with Ugg boots
- Anyone with information should contact police immediately on 020 8345 2710
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The mayor said a post-Brexit visa system was needed to maintain the supply of skilled migrant workers for London's economy.
Peter Barnett made hundreds of trips from his home in Oxfordshire to Marylebone station without paying the full fare.
Police say he may have attacked more children and urged them to come forward.