Updated on 13/12/24 by Abby_OVO
That looks like it could be an old supply pipe. It's capped, has a shut off valve and is right next to the meter so might have been the pipe that used to supply gas into the meter, although it's been replaced by the pipe next to it.
The question is, does it contain gas or has it been disconnected at the other end (where it connects to the gas main, under the road)?
Your gas network company should be able to tell you but I think they will need to come out and check. They will take the cap off an open the valve to find out then will seal it up again. If it is still connected then you need the gas network company to remove it. This could cost a lot. If it is not connected then I'm not sure who is responsible for it. The gas network company should be able to tell you.
I've just googled and it could be an old town gas pipe which was replaced when we swapped to natural gas. If you ask your gas network company for a safety check on it they should check it for free.