This is the image of a man wanted for questioning about a sexual assault onboard a train between St Pancras and Harpenden stations.
He is believed to have started a conversation with two women travelling on the Thameslink line between 1.45am and 2.30am on Friday October 22. A short while later, he leant forward and sexually assaulted one of them.
Officers believe the man pictured can assist with their investigations.
If you recognise him, or have any information, please contact BTP by texting 61016 or calling 0800 40 50 40 quoting reference 2100079526.
Alternatively, you can call Crimestoppers anonymously on 0800 555 111.
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