A home above a shop in East Street has suffered serious damage after a fire started in the mains electric room.
Firefighters and police were called to the maisonette, above the Fat Face and River Island stores just before 9pm last night (Friday, March 4) after the occupiers were alerted by a smoke alarm.
A total of 12 fire engines attended the scene, with firefighters from both West Sussex Fire and Rescue Service and Hampshire Fire and Rescue drafted in to work through the night to bring the flames under control.
No-one is reported to have been injured, and there was a small amount of smoke damage to neighbouring buildings.
When fire crews arrived they found the blaze spreading to the upper floors and roof space of the maisonette via voids and service ducts.
Firefighters wearing breathing apparatus were sent inside to try to prevent the fire spreading to the roof space of neighbouring properties.
They used a special aerial ladder platform brought from Worthing so they could tackle the fire from above.
While tackling the flames, the fire burst through the roof.
More tiles had to be removed to allow the smoke and heat to disperse which helped prevent it spreading along the space in the roof.
Firefighters and police were at the scene throughout the night, including relief crews from across the county.
They were supported by members of the Red Cross who provided refreshments.
An investigation will be carried out today (Saturday) and it is hoped there will be minimal disruption to shoppers.