Classic roosting bars

[Jules27]

Hi everyone!  My first post on here although I've been a chicken owner for about two and half years now and enjoying it!  

We've seen a fox recently in the garden in the early morning - in the run itself in fact - my daughter scared it off after it jumped down from the wall into the netted area.  Thankfully we have a Go attached to the wire run so it wasn't able to get near our three hybrid girls. 

But this morning I found the end of the plastic raincover nearest the coop has been torn at various places, lots of little teeth-holes (I think?!) and one of the toggles pulled off and the water drinker was squint too.  

I suspect the fox has attempted to get access from the top of the run and tried to pull off the cover, probably aiming to get to the small gap there is between the top of the coop and the wire run.  Has anyone else ever experienced this and any ideas how to either deter the fox or reinforce this top area of the coop/run to make sure he doesn't find a weakness?  

I meant to take photos but was in a rush this morning and forgot - I'll post some later for evidence if required!