As is often the case with finding London’s oldest, this isn’t necessarily an easy question to answer.

Hounslow Heath Aerodrome in London’s west was the city’s first civil airfield. First used in 1910 and subsequently by the Royal Flying Corps during World War I, it properly entered service as a civil airfield in August, 1919, when on 25th of that month it became the origin point for the first international flight in the world – from Hounslow to Paris-Le Bourget. That flight, by a de Havilland DH.4A aircraft, was the first in what provider Air Transport and Travel Ltd offered as a daily service.

But despite that historic early role, the Hounslow Heath Aerodrome, which only had rudimentary facilities, had a relatively short-lived life as a civil airport. Croydon in London’s south, home to the RAF Station Croydon and the Waddon Aerodrome, was seen as a more suitable location for the city’s airport.

So, on 29th March, 1920, Croydon Airport opened. While it initially had temporary facilities on Plough Lane (planes apparently had to taxi across the lane to take off and after landing), a permanent terminal – the world’s first – opened near the Purley Way bypass in 1928, making it the city’s first purpose-built international airport (and the biggest and most advanced in the world at the time).

Croydon Airport is also famous for having the first air traffic control system in the world and also boasted the world’s first airport hotel which opened in 1928 (known then as Gate Lodge and today – it’s still in business – as the Croydon Aerodrome Hotel).

The airport was home to Britain’s first national carrier, Imperial Airways, which was founded when four airlines merged in 1924.

During World War II, the airport’s name changed to RAF Croydon – it served fighters taking part in the Battle of Britain – and in 1943 RAF Transport Command was founded at the site and used to ferry soldiers to and from Europe.

After the war, Croydon returned to its role as civilian passenger airport but lack of room for expansion saw Heathrow, founded in 1946 as London Airport and renamed in 1966, take over the role.