Long arms

Hi The Nut,

Get a pair of mole grips.
Grip tight onto the bit inside being careful not to knacker it if it is plastic - and press closed (the beauty of mole grips is that they stay closed tight on the nut once squeezed.)
Leave that inside.
Tighten the outside and as you do the molegrips will turn until they are stopped by the bottom.
Keep tighening the outer bits until happy.
Reach back in and a release the moelgrips.

Bob's your uncle.

 

Mole grip... that´s the english name for my "pinza a scatto". Live and learn.