Father-of-two Andrew Cooper, aged 43, collects NatWest money boxes made by the Burslem firm in the 1980s. And he has tracked down what he believes to be the only two NatWest pigs painted with white tuxedoes.

The original set represented a family of five piggy banks which were given away free by the bank to encourage youngsters to save. They were mass produced until 1990 and since then their popularity has grown among collectors.

In the past two years, Mr Cooper he has spent £10,000 on his hobby and amassed a collection of 150 pieces.

His two latest acquisitions are versions of Sir Nathaniel, the father of the set. The original had a black tuxedo with a red dickie bow and red rose, but Mr Cooper has found a pair wearing white jackets, believed to be the only genuine examples in the world.

He said: "I spoke to other collectors about the white Nathaniels and I started to investigate the story because it fascinated me.

"I put an advert in the Sentinel and had a fantastic response from people.

"The woman who actually painted these two white pigs has been in touch and told me she gave them to her niece, who took one on to the Cash In The Attic television show in 2004.

"It was sold in an auction house in Stoke and since then it changed hands two or three times before ending up with a person in Sussex.

"I managed to track it down about four weeks ago. "For many years, collectors have said the story of the two white pigs is an old wives' tale, but I have proved it isn't."

Since finding the pair just before Christmas, Mr Cooper, a groundwork and building company director from Wigan, has been looking for proof that they are the real deal.

He has had them inspected by 25 Wade collectors, tracked down a DVD of the Cash In The Attic programme and met Wade chiefs to put the final piece of the jigsaw together.

He travelled to Stoke-on-Trent for the first time yesterday to meet the painter who decorated them and visit the Burslem factory.

Staff at Wade told him they also believed the pigs to be the genuine article.

Wade managing director Paul Farmer, pictured below, said: "Mr Cooper visited Wade to meet members of the technical staff in his search for verification of his pigs.

"That is a facility we offer to collectors." Collectors' club manager Jenny Wright said: "These white-jacketed pigs were done as samples on the factory floor and they should not have got out on to the open market to be sold. We have seen white-jacketed pigs on internet auction sites a few times and they should not be there, or they could be fakes."

She said it was not known whether there could be any more white-jacketed pigs.

Mr Cooper said: "I have put a lot of work into this but I feel lucky and privileged to be able to put this story together.

"I am not willing to say how much I paid for them. It's not about money, it's about putting a lid on the story."