The incident happened between 5 and 5.20pm on Saturday 4 March.
The victim was struck near the edge of the station platform, suffering a large and deep wound to his forehead.
Officers would like to speak to the man in the image who may have information that can help their investigation.
Anyone who recognises him is asked to contact BTP by calling 0800 40 50 40 or by texting 61016.
In both cases quote reference number 23000257765.
Alternatively, call Crimestoppers anonymously on 0800 555 111
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