Leave means Leave...

Brexit Party candidate wants out, but also wants to come in...

https://twitter.com/PrehistoricCat/status/1197239943980081152

"I want a cup of tea, I'm f**cking starving"

Oh the irony

But to get hands on, that's assault.

That is a clear cut case of assault by both men who touched him.
Regardless of the fact they didn't want him handing out leaflets, as long as he wasn't a danger or a threat to anyone, they are breaking the law by laying hands on him, never mind physical force resulting in him falling to the ground.
I didn't have the sound up but if he wanted to go in the store for refreshments they have no justification to refuse him. Only if he tried to give his leaflets out inside the store would they be legally within the law to ask him to stop or leave the store.
Security guard should lose his job for his actions and if it had happened to me I would make sure he did!