Police are appealing for witnesses to an incident on Saturday afternoon at the Lombardy Retail Park in Hayes.
A statement issued said that: “Police were called to Lombardy Retail Park, Hayes at approximately 16:15hrs on Saturday, 8 May responding to reports of a man armed with a machete.
“Officers and London Ambulance Service attended and a 26-year-old man was found with an arm injury. His injuries are not believed to be life threatening.
“On Tuesday 11, May a 26-year-old man was arrested on suspicion of grievous bodily harm. He has been taken to an East London police station, where he remains in custody.
Anyone with information is asked to call 101 quoting 4569/08MAY or by contacting Crimestoppers anonymously on 0800 555 111.