TAP Portugal, the Portuguese flag carrier, offers regular, direct flights from London-Gatwick to Lisbon's Portela Airport. The duration of this London to Lisbon flight is two hours and 40 minutes. British Airways also offers direct flights from London-Heathrow. But if time is a major factor in your travel plans, then you are better off with the TAP flight from Gatwick, as delays are much more frequent at Britain's largest airport.
The flight distance from London Gatwick airport to Lisbon Portela airport is 959 miles or estimated flight time is 2 h 19 min.