Gas Pipe Bonding.

yes

Depends if the old metal pipe extends into the building to such an extent it can be touched - typically they're cut back (primarily to prevent any gas leaks outside the building allowing gas to enter the building through the gap between the old and new pipes).

   - Andy.

or like mine when they did the plastic main insertion magic, they wrapped the stub of iron pipe in yellow tape, very badly - worse than when my kids were at kindergarten und wrapped presents for mother's day etc. . But then they also left the meter hanging on the lead pipe tails and I had to run outside an get them back, so not all jobs done by the street main folk are quite to their own standards.

Mike.

Old redundant pipework can even make for a handy 'additional electrode' - when I replaced my lead water suppy pipe with PE I left the old pipe in and bonded and hey presto I'm AMD2 compliant as if by magic! (well on that point anyway.. don't ask about the SPDs.)

   - Andy.

I've also got a handy pipe-shaped earth rod poking out of the floor of my meter cupboard.  In my case, they failed to push the plastic liner up the old gas pipe, and had to resort to relocating the meter to the outside of the house instead.

I think that my gas supply is still in an iron pipe. Certainly the main in the road is 'cos I saw it when the new electrics were put in. The vertical part of the gas pipe seems to be clad in asbestos.

So that's one fortuitous Amd 2 extra earth. The other one is some conduit which supplies my garage pit. It may be above the "waterproof" membrane, but it certainly isn't bone dry.