A plumbing emergency like a leaking main can very distressing. And when I get one it is generally possible to talk the customer through turning the mains off before I arrive.
The last emergency we had was a leaking main in flats. Luckily we got there in under 7 minutes and stopped the water very soon after. TIP: Try and be aware and make a note of where your stop valves are whenever you move to a new property.
The response needed to be quick and it was. Leak was discovered and delt with very promptly.