It has been drummed into all of us from an early age: In an emergency dial 999.

Today the number that saves lives celebrates its 70th anniversary.

Nowadays sophisticated exchange systems run by telephone network companies enable operators to identify the location of the caller and pass on the call to the nearest control room within seconds.

But before the number was launched in 1937 as the first of its type in the world, the picture was very different.

The 999 system was introduced by the London Metropolitan Police as their stations were being overrun by visitors alerting them to emergencies and people trying to call them in the growing trend of using the telephone.

As not everyone knew the number of their local police station, the Metropolitan Police introduced their information room with the famous number of Whitehall 1212.

But calls kept increasing and telephone operators were unable to identify emergency calls from other operator service calls.

It was a fire that prompted government action in November 1935. Five people died, and in the inquiry that followed it became clear that a number dedicated to emergencies only was required.

But which was the best number to use? The choice fell on 999.

The numbers were all at the same end of the dial and thus could be remembered easily and it was relatively simple to convert coin boxes to accept 999 calls without charge.

The system opened in London in 1937 and was spread across the country shortly after.

But ever since it was first introduced a large proportion of callers have rung 999 inappropriately.

The advent of the mobile phone contributed to this problem, with callers accidentally dialling 999 and blocking the system.

In the 12 months to March this year, more than 290,000 calls were made to 999 in Hampshire and the Isle of Wight.

But only 22 per cent of these were genuine emergencies.

Supt Nigel Hindle, head of the call management department at Hampshire police, said: "999 is an effective national service, the use of which is taught from a very young age.

"We ensure that callers to 999 are provided with a professional and reassuring service within ten seconds of making the call.

"We survey 999 customers on a regular basis, to check that we are providing an excellent service.

Last year, 97 per cent of users felt that the call handler was polite, 92 per cent stated that the service was professional, and 90 per cent felt that the staff were helpful.

"This is a significant achievement when in a large number of cases we have to advise callers not to use the 999 service for the non-emergency call that they have made."