Page "Brighton Main Line" Paragraph 16

The Gatwick Express also uses the Brighton Mainline, with non-stop services running between London Victoria and Gatwick Airport.

A train departs in both directions every 15 minutes, with a journey time of 30 minutes.

Six weekday peak-hour Gatwick Express trains are extended to or from Brighton, up to London in the morning ( calling at up to five other stations along the way ) and down to Brighton in the evening.