I'm beginning to think I have an hyper-sensitive sense of smell, or at least I am more alert to it.
I am constantly reporting gas leaks and I always correct, they dig up the road or pavement soon after. I do a fair bit of walking around, so many more chance than most to notice. Unless the smell is very strong, I ignore the first time I smell it in a location. If I smell it again, the smell is strong I ring it in, maybe asking a passerby to confirm they can smell it as I did today.
This one was just outside a Chinese take-away, a rather good take-away as it happens. I was getting it at its strongest by a BT cabinet, or maybe at some manholes near the cabinet. I passed the same location a week ago and noticed it. Today I passed it twice, the second time the take-away were cooking, ready to open and the gas smell was swamped by the food smells, none the less when I got home I put a report in.
There were no signs of any sniffer holes having been drilled, so my guess is that despite it being quite a busy area, no one else had smelled it or if they had, had bothered to report it. I'll bet the footpath there is covered with sniffer holes tomorrow lol