Police are asking the driver of a car, involved in a collision with an eight-year-old boy on a scooter, to please come forward.
It happened in New Church Road at the junction with Pembroke Gardens at about 9.10pm on July 1.
The boy suffered serious injuries and was taken to hospital - he has since returned home.
The driver of a white or light-coloured hatchback car left the scene without stopping.
A Roads Policing Unit (RPU) officer said:
“It is concerning that the driver of the vehicle failed to stop at the scene of this collision where a child was seriously injured and in distress.
“We urgently wish to speak with them about this matter, and are appealing for any residents in the area with relevant CCTV or doorbell cameras, or anyone with dashcam footage in the area at the time to come forward.
“Information can be reported to Sussex Police online or call 101 and quote serial 1418 of 01/07.”