Speed excites the spectator. Crowds love to see fast bowlers in full cry. The sound of the ball thudding into the wicket-keeper's gloves, the batsman hopping and off-balance – his equilibrium disturbed by sheer pace – will always encourage gasps and roars of approval from packed Test match grounds. Fast bowling is all about raw aggression, power and domination. But how fast is fast?

Until the 1998 season in England, no one really knew. There had been attempts to measure the speed of bowlers before, using the kind of radar guns police point at speeding cars. There were trials in the 1950s when Frank Tyson was in full cry, and again during World Series Cricket 20 years ago when Jeff Thomson was declared the fastest of all. But the technology was uncertain. And a similar exercise at the Lord's Test against Pakistan in 1996 produced implausible results and public derision. The machine was soon switched off.

However, in the last English summer, the technology took a giant leap forward. The Yellow Pages Speedster appeared at Test grounds, telling spectators – and the players – the speed of a delivery moments after it had been bowled. And this time the technology seemed unassailable. It was still pooh-poohed, mainly by former quick bowlers. Surely, the argument went, there are enough visual keys for the spectator without an electronic readout. But people like to grasp something tangible: how fast their car gets from nought to 60 mph – or how often Allan Donald bowls at over 90. It was a popular innovation.

The Speedster is a spin-off from the arms trade. It was developed by a firm in Stellenbosch, South Africa, using technology originally intended to measure the speed of bullets. The breakthrough, it is claimed, is that the speed is measured in two dimensions rather than one. The system measures the vertical speed of the ball as well as the horizontal speed, which gives a much truer indication of its actual velocity. What that means in practice is that two people sit huddled round a bank of computer screens which receive information from a small box behind the bowler's arm. A computer 400 times faster than the average home PC verifies all the readings, and only then will it allow the speed to be displayed. All this takes about a second, by which time the batsman can check whether he has faced a very fast delivery or not – as if he did not already know.

But the bowler really might not know. During the series against South Africa, when Donald was confirmed as comfortably the fastest bowler on either side, David Lloyd, the England coach, mischievously suggested that the Speedster ought to be turned down when Darren Gough was bowling to encourage him to try even harder. For most of the summer, Donald regularly clocked 90 mph, and averaged 86. Gough only occasionally touched 90. For other, slower, bowlers, it could all be a trifle embarrassing. There was Donald exploding the ball into the turf, and there was Angus Fraser, steaming in with every ounce of effort he possessed, to get the needle up to about 78. Still, Gough and Fraser had the last laugh: England won the series.

Prior to the Speedster, cricketers talked of pace in terms of yards, not mph. And this concept is useful to put the new-fangled device into context. Bowlers have often yearned for an extra yard of pace: over the 20 yards the ball travels between bowler and batsman, the yard is significant. The extra yard makes batsmen hurry. Get two yards quicker, and that is some achievement.

The difference between Donald's average of 86 mph and Fraser's of 78 is about ten per cent – or two yards. It may not sound a stunning statistic but, in terms of professional cricket, it is significant. Many spectators were surprised to see that players they regarded as trundlers were also breaking the motorway speed limit: Hansie Cronje, for instance, averaged 74, but that is another half-yard slower than Fraser.

There is far more to bowling than sheer speed, as Fraser showed. But the Speedster is likely to increase the emphasis on raw pace. A 100 mph delivery would be two yards faster than Donald. That is fast, very fast. What price someone breaking the barrier? If it happens, the crowd's applause is likely to be wilder than anything that greets a more conventional century.

Paul Allott bowled in 13 Tests for England in the 1980s without ever quite reaching 100 mph. He is now a freelance writer and commentator on Sky TV.

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