From central London, the fastest way to get to Gatwick is by train

https://www.scribd.com/document/1077066259/Heathrow-to-Gatwick-Airport-Transfers-Coach-Taxi-or-Train-174457

From central London, the fastest way to get to Gatwick is by train. Gatwick Express runs non-stop from Victoria, with frequent departures and a journey time of about 30 minutes.