While Heathrow is the most famous, several other airports in London are used by different routes and airlines.
London City Airport is the most commonly used for business trips within Europe, as it is the closest to the city centre. It is a small, easy-to-use airport and my favourite, although tickets are often slightly more expensive.
This time, I took the earliest flight of the day at London City Airport, leaving for Rotterdam at 6.30am, so I arrived there by taxi (Bolt) at 5.30am. As you can see, it was still dark.