British Airways A320 G-GATJ operating BA2714 London Gatwick – Malaga stopped the climb at 9,000 ft to the north of Portsmouth when the aircraft failed to pressurise, circled over Biggin Hill to burn fuel and then returned to London Gatwick for a safe landing. During the evening the aircraft positioned London Gatwick – London Heathrow for previously scheduled maintenance as BA9279. This is the first visit of a Gatwick based CY171 A320 to London Heathrow.