Police are investigating after a boy was attacked while onboard a Thameslink train between Blackfriars and Sutton.
British Transport Police officers say a woman was sat next to the child before she was seen on CCTV assaulting him at around 10pm on May 4.
It is believed the woman pictured may have information which could help in the investigation.
Anyone with information is urged to contact BTP by sending a text to 61016, or by calling 0800 40 50 40 and quoting the reference 703 of 04/05/2018.
You can also contact Crime Stoppers anonymously on 0800 555 111.
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