This is a joke surely? Heathrow is one of the busiest airports in the world, and certainly one of the busiest International airports. It started life after the Second World was, but after the original Gatwick. the main London airport was at Croydon, and this closed in the 1950's. Terminal 2 was built in the 50s, Terminal 3 ws built in the early 60s, and Terminal 1 came into being in about 1969, Terminal 4 came about in the eraly 80s. The South Terminal at Gatwick was built in the late 1950s, and the North Terminal was opened a little over 10 years ago. Of far greater concern is that Heathrow is only a two runway field for most of the tme. There is another which is used in cross winds, but it is not long enough for Long Haul take-offs. The notion that it was built as a Gatwick replacement is actually funny.