What no gas

The old gas tank holders should be preserved as works of art, shouldn't they? I've never worked out how they go up and down or how they get re-filled but they are a part of our history so could they be used for anything else other than holding gas? Suggestions on a postcard (or in comments) please.

This one was on Greenwich peninsula and I love the geometry of the iron against the natural curves of the tree.

Raining all day so a quick check outside and a quick trip to get some straw and to the garden centre other than that it's rugby & beer now and Curry & wine tonight...