For most of the past 40 years, mystery has surrounded the whereabouts of the ball used in the famous over. Various rumours suggested that more than one ball was used, one of the sixes landed in a passing carriage of the Mumbles light railway (even though that stopped running in 1960) and the ball had disappeared from the museum at Nottinghamshire's ground.

The formal return of the ball by the Pontardawe schoolboy Richard Lewis to Garry Sobers took place at St Helen's on the morning of Monday, September 2, 1968.

The alternative story to the one involving the museum is that the ball was given to the then secretary of the Nottinghamshire Supporters Association John Gough and was kept in the Eddie Marshall Bar at Trent Bridge.

Marshall was chairman of the association which was based in the bar. The ball passed into the hands of Gough's successor Josie Miller, who kept it in her make-up drawer until she decided to sell it two years ago.

In 2006, the ball was passed to Christie's in London, via Sobers' agent, Basharat Hassan, a former Nottinghamshire star who now runs an events promotion company.

Wynne-Thomas and his counterpart at Glamorgan Dr. Andrew Hignell discussed the intended sale on the telephone. Hignell travelled to London to verify the details of the match and was shown the ball.

At the auction in November, the ball was described as a "red leather Special County cricket ball, manufactured by Duke & Son, Nottingham, signed 'G. Sobers' (seam stained, quarter seam split, general scuff marks); with a certificate of provenance signed by Sir Garfield Sobers, stating 'that this signed cricket ball was bowled during the over in which I [Sobers] hit six sixes off Malcolm Nash."

According to Christies, three separate balls were used in the over.

The auctioneers had put a guide price of between £5,000 and £8,000 on the ball which was bought by an anonymous bidder for £26,400.

When news of the sale reached Wales, doubts began to be cast on the ball's authenticity and The Independent on Sunday's Andrew Tong reported on the resultant disquiet among Glamorgan players.

His article – headlined 'Howzat for a mystery: is this the most famous ball in cricket?' – pointed out that the ball sold at Christie's was made by Duke & Son of Nottingham but in 1968, Glamorgan only used balls made by Stuart Surridge.

"I think the authenticity of the ball sold at Christie's is questionable," says Glamorgan all-rounder Peter Walker. "The only person who can say with any authority whether that ball is the right one is the bowler, Malcolm Nash."

"I was really surprised when Peter called to tell me about the ball in 2006," says Nash. "I thought it was in the museum at Trent Bridge but I then heard it had disappeared.

"When we were playing at home, either Tony Cordle, our other opening bowler, or I would go into the umpires' room and select the balls.

It's a fact that the ball we used on that day was a Stuart Surridge ball because Glamorgan never used anything else for home games. There have been various debates and arguments about whether it was changed – I can assure you it wasn't."

In the 1969 Glamorgan Members Newsletter, a review of the previous season contained a report on the meeting between Richard Lewis and Garry Sobers when the ball used in the over was taken back to St Helen's.

The report stated: "Glamorgan presented this ball, which was made at the firm of Stuart Surridge, the former Surrey captain, to Nottingham to reside in a place of honour in their Sporting Museum."

Six of the Best – Cricket's Most Famous Over by Grahame Lloyd Published by Celluloid Ltd and available from this week Price: £14.99