From Croydon, hop on Southern or Thameslink from East Croydon station

https://rylanfdkl454.theglensecret.com/how-to-reach-gatwick-airport-from-london-bridge-station-1

From Croydon, hop on Southern or Thameslink from East Croydon station. Trains to Gatwick are frequent and fast, often taking less than 20 minutes platform to platform.