Countdown to the final: The curious case of the funny-shaped ball

It is the subplot which has attracted almost as much scrutiny as England's improbable progress through the Rugby World Cup final: are the tournament's balls tainted?

This year's Rugby World Cup has hardly been short on drama. There has been England's extraordinary rebirth from national disgrace to feted heroes; the scintillating speed of South Africa's Bryan "The Man Who Races Cheetahs" Habana and the bone-jarring tackles of hirsute Gallic pin-up boy Sebastien Chabal.

But nothing that the human endeavour on the pitch can provoke matches the furore and hype surrounding something that has hitherto served an unassuming role as the mere instrument of man's glory. Whether by boot or in the outstretched arms of a triumphant try scorer, we are talking of the humble match ball.

For this year, the celebrated oval that gives the game much of its distinctive character (as well as spawning thousands of unfunny car stickers about rugby being a game played by men with funny-shaped balls) has been the centre of intense scrutiny.

The reason for the sudden interest is a flurry of misses from some of the game's biggest and most accurate kickers, including England's very own Jonny Wilkinson. Doubt first crept in when the All Black's robotically accurate Dan Carter failed to convert five out of nine kicks at goal in New Zealand's 40-0 win against Scotland. Then it was the turn of Wilkinson's golden boot to fail when he squandered three out of seven penalties in England's quarter-final against Australia.

Comments made by the players in post-match interviews seemed to pin the blame on the British-made Gilbert Synergy match ball and the tournament organisers ordered an immediate investigation. No design faults were found but some of the balls were discovered to have been inflated beyond the pressure recommended by manufacturers.

Wilkinson, given unprecedented access to all six of last Saturday's semi-final match balls – correctly inflated that time – eventually declared himself a workman happy with his tools, though against France – the last 10 minutes aside – his kicking performance once again failed to convince.

For Ian Savage, 28, a sports engineering graduate who works as ball engineer for manufacturer Gilbert, these have been trying times. For it fell to him to personally weigh and measure each of the 288 bespoke match balls by hand for this year's tournament. It was a process he repeated four times for each ball.

Having spent the past three years immersed in every detail of creating the ideal ball, the criticism was hard to take but he remains philosophical. "Players are put under a lot of pressure to make statements but that is the world we live in. It was just a couple of comments taken out of context. It is just one of those things. You cannot fight back in the media but now the facts are starting to come out the reports are becoming more balanced," he said.

As a result of the controversy surrounding the ball, Gilbert has adopted a policy of trying to tell the world as much about their ball as they can. They are happy to discuss everything from the painstaking development process to the number of wax-coated polyester thread stitches that goes into each one – 320 if you were wondering, or 80 to secure each of the four panels.

But some details of the production process remain firmly under wraps. Exactly where the ball is manufactured is tightly guarded secret. Fears over industrial espionage meant Mr Savage was prepared to confirm only that the balls were made "somewhere in England" but refused to elaborate any further. "If I narrowed it down more than that people might guess," he said.

The reason for the cloak-and-dagger stuff is the patented "pimple pattern technology" a series of raised bumps that allows the ball to be handled comfortably while not interfering with its smooth aerodynamic flight. Then there is the top-secret process for rubberising the markings on the ball that has eradicated any hint of slipperiness associated with the lettering process.

It is all a far cry from the early days of the game and Gilbert prides itself on its association with the sport at its inception. According to the official company history when, in 1823, William Webb Ellis "with a fine disregard for the rules of football as played in his time first took the ball in his arms and ran with it" the ball in question was a Gilbert.

For the company's founder William Gilbert owned a boot and shoemakers in the high street next to Rugby School and had begun a lucrative sideline of fashioning four-panel, hand-stitched leather casings, complete with a real pig's bladder for Thomas Arnold's young charges just next door.

Back then, the ball was shaped more like a plum than the perfect oval it is today and each one was wildly different. The worst job in the Gilbert workshop was inflating the uncured pig's bladder by blowing down the stem of a clay pipe, a task that required powerful lungs and an even stronger constitution as the porcine viscera was often extremely smelly.

One young man who excelled in that malodorous task was Gilbert's nephew James, who represented the company at the Great Exhibition of 1851. The ball making remained a family enterprise until 1978 by which time it had pioneered new technologies and become the match ball of choice across the rugby-playing world. After a period of some turbulence, Gilbert eventually returned to its spiritual home in the Warwickshire town after being bought by another long-standing family sports business, Grays.

Today, Gilbert turns out some 15,000 match balls a year, all of them hand-made. But the responsibility of producing the World Cup balls falls to an elite band of 10-12 predominately male craftspeople based at the company's secret location in England.

The original leather press from the 1800s is still used to stamp out the traditional leather balls although the science for the process has moved on rapidly.

The present match ball is made in three stages: an outer rubber compound; a poly-cotton inner and inside that a bladder of natural latex that, when inflated to the required pressure of nine and a half lb per square inch, would measure the size of four family cars if it were not compressed by the hard case of the ball.

"The average Joe who is in the stadium or watching it on television would never normally have even thought about the ball," concedes Mr Savage. But for those responsible for their manufacture it is an ongoing and highly technical process. The key is balancing the payoff between handling and kicking. A smooth ball is easier to kick but more slippery to handle.

And then – crucially for Jonny Wilkinson and the England fans whose hopes ride on his shoulders – there is the degree to which the ball deforms around the foot when it is kicked.

In simple terms, the softer the ball is the further it goes but the more difficult it is to aim. A harder ball is more difficult to kick but easier to aim.

One of the men responsible for getting the present ball in match shape was David Curtis of Sports Engineering Research at Sheffield Hallam University, one of the world's leading centres for sports ball technology.

Before the Gilbert Synergy went before the International Rugby Board for approval, it first had to undergo rigorous tests in the laboratory of Mr Curtis. First it was passed through a non-contact laser scanner to create a three dimensional computer model. From that, experts could analyse the complex aerodynamics of the spinning rugby ball until eventually they could create a consistently true-flying ball.

Naturally the controversy this World Cup was keenly felt in the Sheffield laboratory.

"When I heard the comments come out from Jonny Wilkinson that the ball seemed to move when there was no wind I thought 'that's interesting'. There is no such thing as no wind," said Mr Curtis.

"Even if the breeze is imperceptible at ground level at the height it is kicked there will be some kind of velocity. There is always circulating air and eddies higher up caused by the shape of the stadium and the influence of the crowd."

Ian Savage believes Gilbert has done enough to silence its critics and enjoys the full backing of the competition organisers and the players. He is now setting his sights on the next World Cup and is already building the prototype for the next ball. And he says there will be no nerves when England and South Africa run out on to the pitch at the Stade de France on Saturday night.

"You know when you get the World Cup contract that all the work you have put in has been worth it and you are recognised as the maker of the best match ball in the world – they wouldn't pick it if it wasn't. It has been such a big part of my life and it feels very worthwhile when it is used at the very pinnacle of the sport."