Duetto Locking Water Tank Cap

Not having used the water tank on my Duetto for a couple of years I thought it time to give it a clean. However I cannot get the filler cap off. The key does unlock it but despite turning the cap round several times it will not come away from the van. Has anyone else experienced this and found a solution? I wondered if the thread had gone.

Try pouring warm water over the cap, might just expand the plastic

We sometimes have the same problem. Its a tricky design because you can't get enough grip on the cap to ease it out. Use a screwdriver to gently put some "out" leverage on the cap as you turn it.

I find it helps to push in on the cap while turning it, it's a bayonet fitting so no thread involved just a 1/4 turn and its off.
Graham