Sometimes you just don't realise just how absolutely, overwhelmingly, mind-bogglingly filthy.......... your patio is until you turn a pressure washer on it.
Here is some before and after.
And it's great fun; a real boys toy!
Especially when an incautious pigeon gets a little too close. No pigeons were harmed etc, but he is probably the cleanest he has been since the day he hatched.