Transfer from London Heathrow to London Gatwick
 

What is the easiest way to get from Heathrow to Gatwick?

Helicopter.

Seriously.

Don't know about availability.

Congratulations, you have chosen one of the worst inter-airport transfer options possible considering the time it will take you to get your stuff at Heathrow (in all likelihood) and the time it will take to get to Gatwick and the time you will need before your next flight for check-in.

There is a direct transfer bus. http://www.nationalexpress.com/where...w-airport.aspx

There is no direct train.

I hope you have allowed yourself at least 4 or 5 hours for this - or you may well not make it.

What day and time do you land @ LHR? That will make a BIG difference to the answer.

There's no helicopter.

Buses take between 50 min (from Heathrow T5 to Gatwick North) to 75 mins (from T1 or 3 to Gatwick South) and leave every 15 mins or so, though you normally need to add another hour to the transfer time to guard against traffic problems, and need to assume a total of 4 hrs from landing to takeoff for immigration at the arrival airport and security at the departure airport.

It's rare for a privately booked car to offer a materially faster time (there's only one way they can go, and cars can't travel any quicker than buses), but if you want one for reassurance, use one of the prebooked services (like justairports) recommended here.

In theory, "through" tickets (especially on BA and its One World partners) requiring a change of airport are issued only with enough time intervening to allow this connection, and come with a guarantee you'll be booked on the next available flight if you miss it. Though BA weasel when you push them on this, there's never been a complaint here of an airline failing to honour this guarantee.

All of which said, same-airport transfers at Amsterdam, Frankfurt, Munich or Zurich are a great deal easier, and few people would argue that the financial saving you might make via London is worth the hassle. Even in provincial Britain, most people would rather fly from their local airport to Amsterdam, Dubai or Frankfurt and change planes there than hang around London's motorways.