The British Transport Police is investigating the incident that took place at Golders Green station at around 4.30pm on August 12.
A man was reported to have been racially abusive towards another passenger onboard the train, which was heading northbound.
The force has now released a picture of a man they wish to speak to, whom they believe could help with the investigation.
A spokesperson said: “Officers investigating a racially aggravated incident on a Northbound Northern Line train to Golders Green station are today releasing this image in connection.
“At around 4.30pm on Tuesday 12 August, a man was racially abusive towards another passenger.
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“Officers believe the man in the image may have information that could help their investigation.”
Anyone who recognises him is asked to contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 516 of August 12.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
