It seemed a good idea, given that we're in a drought. The water isn't coming out all that fast — about as fast as a bath tap — but it's been doing it for a couple of weeks and is gradually getting faster. A second crack has now opened up, and possibly a third.
Anglian Water's web site for leak-reporting is pretty good, but it only let me upload one photo. This is the one I chose:
It isn't exactly informative, but they didn't allow videos. That said, the video isn't exactly informative either.
Anglian Water assure me that they'll have an engineer look at it within two weeks. I guess this means I can expect that the street's water will be turned off for half a day two weeks from now.
Fortunately, I'll be on holiday two weeks from now so I don't care.