Avoid last-minute stress by aiming to arrive at Heathrow two to three hours before departure; select the fastest route

https://www.scribd.com/document/1074920514/Getting-to-Heathrow-from-Gatwick-Easiest-Inter-Airport-Transfers-178501

Avoid last-minute stress by aiming to arrive at Heathrow two to three hours before departure; select the fastest route available for your time window.