For the last few days now, I've smelled natural gas whenever I'm outside the front door. In a potentially foolhardy case of "out of sight, out of mind" (or in this case, out of smell), I kept forgetting to do anything about it. It was particularly strong this morning though, and I could even smell it inside the house. So I called the city council, who told me to call 111 (that's the emergency number).
The Fire Service arrived a couple of minutes later, bearing two firemen (one of whom was the spitting image of that guy from the TV show The Guardian - yes Virginia, there really are cute firemen).
It turned out that the gas pipe which has been poking out of the front lawn all these years had somehow lost it's cap, and was leaking either gas or the odourant which is added to make leaks detectable. However, it wasn't a danger to the boy (who is in the habit of lighting his cigarillos as soon as he steps outside the house).
Solution? They plugged it up with bits of soap which I fetched from the bathroom, and promised to put some pressure on the local gas supplier.