Mains gas "safety RCD" are likely to become the norm within about
10yrs.

You can already buy a valve which on full-bore escape will cut off the
gas.
More intelligent devices monitor appliance usage and thus will cutoff
on slight leaks.

They should really be fitted in the pavement outside rather than
internal pipework.
Lead mains gas incomers still exist, under the stairs and complicate
fire fighting.