If you can't help it and your tennis racket is always with you, even if you travel, check out the four tennis courts at the Tanner Street Park in Bermondsey. They're FREE to use. If they're all taken, just queue up and wait for you turn.
The park is small but tidy and clean. Locals are often hanging out with some drinks or walking the dogs, there's always a chance to meet someone while you wait for your turn before hitting your aces on the court.
And if you're lucky, you can spot squirrels jumping around the trees, or chased by the dogs!
4 Tanner St, London SE1, UK