The incident occurred at around 6.18pm on Saturday, June 15th.
The 19 year old motorcyclist was travelling on a green Kawasaki bike on the Winchester Road, near the entrance of the Clock Barn.
During the collision, the motorcyclist came off his bike, was knocked unconscious and sustained injuries to his left leg.
It is believed the BMW was grey and would have sustained significant damage to the offside rear passenger door, window and trim.
Did you witness the collision?
If you have any information or if you have dash cam footage of the vehicles, please get in contact by calling 101, quoting reference 44190206128.