Officers from the Roads and Transport Policing Command are appealing for witnesses to a fatal collision near Mornington Crescent Underground Station.
Police were called at around 01:35hrs on Saturday, 19 November to reports of a bus and a pedestrian in collision in Hampstead Road, NW1 (opposite the station).
Officers and London Ambulance Service attended. The pedestrian, a 47-year-old man, was pronounced dead at the scene. Next of kin have been informed.
Whilst officers believe they know who the deceased is, formal identification has not taken place.
A post mortem examination will be scheduled in due course.
The driver of the bus - a route 134 - stopped at the scene and is assisting police with their enquiries. The driver was not arrested.
Officers from the Serious Collision Investigation Unit (SCIU) at Alperton Traffic Garage are carrying out enquiries into the circumstances of the collision.
They are appealing for any witnesses or anyone with any information to contact them.
Detective Sergeant Chris Osborne, from the SCIU, said:
"We are still unsure as to exactly how this collision happened and would like to speak to anyone who saw what happened. We know the bus had a large number of passengers on it at the time and there were also a number of people waiting at the northbound bus stop opposite the tube station."
Anyone who can assist police is urged to contact the witness line on 020 8991 9555.