A man has been arrested this morning on suspicion of grievous bodily harm and kidnap.
Witnesses spotted a Metropolitan Police helicopter flying over the River Thames between Kew and Brentford after officers were called at about 3.45am.
Officers had been called out to reports that a man had been seriously assaulted.
Access to the Thames Path was sealed off on the northern side of the river with an officer stationed by the alleyway off Brentford High Street, next to the Waterman's Arts Centre.
Following a search of the area a 37-year-old man was arrested.
A spokesman for the police said the victim later went to a west London police station and was helping with the investigation.
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