Police have released a photo of a woman they wish to speak with after a boy was assaulted on a train to Sutton.
The attack took place on board a Thameslink train shortly before 10pm on May 4.
During the journey from Blackfriars to Sutton, a woman was seen on CCTV assaulting the boy who was sat next to her.
Officers believe the woman shown in this CCTV image may have information which could help them investigate.
If you know who she is, contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 703 of 04/05/2018.
Or you can ring Crimestoppers anonymously on 0800 555 111.
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