The incident happened in an alleyway near West View Road at around 3.50pm on Friday 12 July 2024.
The victim states he saw an altercation involving a man and a woman but, when he tried to intervene, was assaulted and threatened by the pair.
Officers are now able to release a CCTV image of a man who may be able to assist them with enquiries.
Anyone who recognises the man, or who has any further information, is urged to call the west Kent appeals line on 01622 604100, quoting reference 46/116016/24.
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