Planning from East London? Take the Elizabeth line or Tube to Farringdon or London Bridge

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

Planning from East London? Take the Elizabeth line or Tube to Farringdon or London Bridge, then transfer to Thameslink for a direct ride to Gatwick Airport station.