The lack of any definitive guide to what is down there makes the task primitive in the extreme. Progress is often made by informed guesswork; mistakes frequently happen - a power failure, a ruptured water main or a split cable. British Telecom admit that records of even their relatively recent network cannot be relied upon.
There are stories of water diviners being employed by some gas and water companies to locate "missing" mains, people are so desperate. The cost to the nation of digging up the streets to get at a burst water pipe, a leaking sewer or faulty cable is at least pound;3 billion a year; some believe it might be double that.
Annually, there are about 4 million holes dug in the UK's roads to get at the utilities buried beneath. Glasgow's Great Western Road was dug up 223 times in a single year - London's Oxford Street 288 times. If a way could be found to cut back on the exploratory operations, to turn a clumsy search with a digger or spade into something more akin to microsurgery, the country could save a fortune. Experts have proposed three-dimensional digital maps to mark every line, electronic tags to keep an eye on new ones, and smart pipes that could be easily located, remotely monitored and even heal themselves when damaged.
* 482,000km of electricity cable
* 396,000km of water pipes
* 353,000km of sewers
* 275,000km of gas pipes