This Swift was found on the ground in North London. It had probably hit a high structure (glass, wires).
Once grounded, it is very difficult for swifts to take off as their wings are too long and their legs very short for clinging to vertical surfaces. It was undamaged.
After a rest and some food, it was returned to the spot where it was found. When thrown gently up into the air, it was able to take flight again.
Swifts have extra long wings and it is said that they are the only bird which, in flight, can flap each wing independently.
The photo on the right appears to show this.