A 46-year-old man died after suffering stab wounds during an incident at a block of flats in Hayes last night (Thursday).
Police were called to St Dunstans Close shortly before 9.30pm following reports of a disturbance.
Officers found the man with stab wounds to the torso.
London Ambulance Service and London's Air Ambulance attended the scene and the man was taken to a central London hospital where he was pronounced dead at 11.34pm.
The Met has not officially named the man but Darren Thrower, of Oxford, has been in touch with the Uxbridge Gazette and named the victim as his brother, Paul.
A post-mortem examination is yet to be scheduled. The Homicide and Major Crime Command are leading the investigation.
The 16-year-old boy was arrested by Hillingdon officers and is in custody at a west London police station.
