it might just be a 13mm hex key then in that case.

My halford tool kit goes up to 10mm hex key which way way to small, and thinking about it maybe it is a 13mm hex key. Is this usually something special u have to buy for the cossies sump? The nut itself is new with a new little washer that u can see pressed against the sump, problem is i aint got the correct hex key.
I thought the sump plug was supposed to be the same as a escort turbo i.e a 13mm nut.

Will pop down halford and get meself a 13mm hex key, hopefully that should be the right size

cheers mate