On the 6th july of this year there was a reported short interest...

On the 6th july of this year there was a reported short interest of 29m shares. On the 9th of July this was 3m. On the 11th Capital announced they had reduced their long position by 29m shares.

If the short position reports are to be taken on face value, then in the first week of July the must have been buys trades of 26-29m shares. POf course there was not.  What is more likely is that Capital used their prime broker to short so they did not need to undisclose change in substantial shareholding, and when they finished the programme they closed out the short with a cross. Of course, there was never a true short position in the market - just a reduced long position. I assume Capital assumed the market impact cost of announcing reductions in the substantial holding was going to be greater than the the market impact of the increasing short.

So by the same token, as an institional investor I could hedge a long positon using short contracts, knowing I could costlessly cross the positions if I needed to.  Although I do struggle what the advantage in doing this is, other than a sleathy liquidation, or pushing the price down in order to reduce subsequent acquisition cost.

Nonetheless,  "whoever I am" I do take the time to understand what I am talking about, and I do not undermine other posters from a position of ny own ignorance. It is not pleasant or helpful.