I’ve seen it a few times - but let’s just use his own words. Firstly, the Oldham Times states -

In the videos, Harratt can be seen picking up a chair and throwing it towards the other group of people, where it hits a woman in the back of the head and she falls to the floor.

So she didn’t ‘slip’.

And then he himself is quoted as saying -

He then claims a chair was thrown at him, and he threw it back, not meaning to hit the woman.

So he is admitting to throwing it and hitting the woman- so let’s not make it out to be anything that it isn’t.