Why Jonny's radar has been on the blink in France

The defending champions are calling on the organisers to ensure that the six balls earmarked for Saturday night's semi-final against France are not pumped beyond the limit recommended by their British manufacturers.

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Up and down: Wilkinson kicks a penalty against Australia but his success rate has fallen

Checks carried out privately by England's technical staff have revealed what they consider to be the reason for Wilkinson's hitherto inexplicable drop of almost 20per cent in his kicking success ratio.

Every ball at the tournament comes with instructions from official suppliers Gilbert to be pumped to the 'optimum' level of 9.5lbs per square inch.

England claim that the balls for their opening match, against the United States in Lens last month, showed

10.5lbs per square inch on the pressure gauge and that others may have been even more pressurised.

World Cup directors have already ordered an investigation into earlier complaints from New Zealand's Dan Carter and found nothing wrong with the ball. Now, in the light of a more specific complaint and Wilkinson's increasing concern, they will send reminders to the match commissioners on the pressure of balls for the final two weekends as the best World Cup of all rolls on towards a thunderous climax.

'We can confirm that some balls were found to have been over- inflated,' said Greg Thomas, the tournament's director of communications.

'When that happens, its characteristics change. Information on the correct pressure is being sent out to the appropriate people. This is not a new ball but a make from the No 1 manufacturers which has been used all over the world for some time.'

A ball at the wrong pressure is liable to play havoc with any place-kicker.

'To someone like Jonny, an increase in pressure of one pound per square inch changes the whole feel of boot on ball,' said one former international goalkicker.

'The ball loses shape and you get less energy into it. It's about the same sort of difference as driving a highperformance sports car with the wrong tyre pressure.'

Wilkinson, whose importance to England was never more pronounced than when he kicked eight goals to account for all 24 points in the semifinal win over France four years ago, went into this World Cup with a career strike rate in Tests of marginally above 80 per cent.

In three matches here he has missed nine shots at goal, compared to an average of fractionally more than one per game over the four-year period leading to the last World Cup.

His current percentage success of not much more than 60 is abnormally low, all the more so compared to Chris Paterson's flawless record for Scotland — 17 out of 17.

Ever ready to blame himself, Wilkinson is the last player to find fault elsewhere. But the high inflation theory will go a long way towards helping him understand why some of his penalties missed the target against Australia last weekend and why, more alarmingly, Wallaby captain Stirling Mortlock missed the late long-range attempt to win the match.

'It was a damned fine kick,' Wilkinson wrote in his newspaper column about Mortlock's do-or-die effort. 'With the balls flying the way they are, he has real sympathy from me there. As a kicker here you are not completely accountable.

'Sometimes it's like you are almost hitting and hoping and kickers just never do that.

'This is a difficult subject - I don't want to make a big deal out of it but, in kicking, you naturally want to control as much as you can. You cannot ever control the wind or the pitch conditions. It seems to me, at this tournament, the ball is another of those.

'When you can't control something like that it is very difficult. I'm aware that some kickers, notably Chris Paterson, have been extremely successful.

'I feel I've got a few kicks right and still been punished by seeing them go wide. On Saturday I missed three from seven, one of those I knew immediately I had executed wrong but I was happy with the other two.

'The wind made it very tough. But if the ball moves in midflight you have to work out if it's the wind, the ball or yourself. The good news is that I've got all week to perfect it.'

Gilbert's extensive research into their ball included laboratory tests and practical demonstrations by former England fly half Paul Grayson. They reached a verdict, accepted by the World Cup, that 'any perceived differences can be explained by incorrect inflation and natural wear and tear. This has been explained to all the teams'.

England have also raised private concerns over the distribution of match balls. Six will be set aside for use in each semi-final this weekend with each team given two each at the start of the week, with the last one on match day.

England only received theirs less than an hour before kickoff against Australia which left Wilkinson precious little time for practice.