Yes, how gas was supplied, has varied since it was first installed...
As above, it looks like a very old gas appliance stub, where a bit of rubber pipe was pushed onto the stub, leading to the appliance, with a tap to turn the gas on. Normally, I would expect to see one, indoors, adjacent to an appliance position, like an old gas fire. Why that is outdoors, I cannot even guess. Probably best to ask Transco or whoever, deals with gas pipes in your area, if it is live.
Looks like it's possibly some sort of test point, but in my opinion you need get your supplier to check if it is live or dead and cap it off to prevent future confusion.
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