There are many ways to be active outdoors in London - walk, run, cycle, swim, even sledge - each offering a fresh perspective on the city.
There is an obvious overlap between running and walking routes, so many of these tips are valid for both. As well as the obvious routes within London's parks and green spaces, why not try routes that connect them? London Greenground Map by Helen Ilus shows how the parks and open spaces are connected. It uses a Tube Map style, so while it's a great starting point to gather inspiration, you might then want to plot your route using an online map.
If you are starting out, ParkRun is a great place to be inspired. There are almost 50 Parkrun routes in London, all exactly 5km. Many involve various laps or a return journey over the same route, so they can easily be broken down into smaller chunks. Although the official events are held on a Saturday morning (on hold at the time of writing due to covid-19 restrictions), the routes are available online so you can have a go any time. For more advanced runners, Strava has a wealth of routes created by users of lengths covering all fitness levels, as well as monthly challenges for subscribers.
Stand Up Paddle Boarding (SUP)