Gordon Brown has denied ever hitting anyone. Excellent. Well done. But it wasn't one of the allegations made against him in any case.
No. 10 categorically deny that Sir Gus O'Donnell ever instituted an inquiry into Gordon Brown's behaviour. That's nice. But again, it wasn't one of the allegations made - all Rawnsley says is that O'Donnell heard informally about Brown's behaviour and gave a private warning to the Prime Minister.
So, when in doubt, just refute a few allegations that weren't actually made