Mold Crown Court heard how Thornton set up a fake company with fictional directors to help him make a bogus sale, on which he claimed VAT.

Thornton denied being concerned in the fraudulent evasion of VAT, and furnishing false information that Park Royal Vehicles Ltd was entitled to claim back £32,392 in VAT, in July 2005.

He did not give evidence in his own defence during a trial lasting more than two weeks, but in an interview said he had done nothing wrong.

Thornton was convicted by a jury and was told by Judge John Rogers QC it was a gross breach of trust.

“As an experienced VAT officer, you deliberately used your knowledge of the VAT system to carry out a sophisticated fraud, depriving Customs and Revenue out of something in excess of £32,000,” the judge told him. “This is a gross breach of trust by a public servant.”

Thornton showed no emotion when the guilty verdicts were returned.

The prosecution told the court Thornton ran the Bodfari and Mold Railway Society and set up another company called Park Royal Vehicles Ltd.

He pretended there was a £180,000 sale of rolling stock between one and the other to get the VAT back.

He was the only signatory on the accounts and the “directors” of the company he set up were celebrated Victorian railway engineers.

In March 2001, Thornton bought land at Bodfari which contained a third of a mile of the former Mold to Denbigh Railway Line, where he set up the Bodfari Railway Centre.

Some items, including a multiple diesel unit, a carriage, and some track, were placed on the site but the project turned sour when he was refused planning consent and an appeal was thrown out.

Since 1989 Thornton had been working for Customs and Excise dealing with VAT. He also ran a photography business.

Graham Knowles, prosecuting, said Thornton had the VAT number of his photography business transferred to the Bodfari and Mold Railway Society, giving his Llanddulas address.

The group bought various items of railway, and then VAT forms began to be received in the name of D. Owen and later David Owen, giving an address in St Chad’s Way, Prestatyn, where Thornton had previously lived with his mother. He also gave a London address at one stage.

When the VAT payment was made, it promptly disappeared from the account of Park Royal Vehicles Ltd, and much of it was used to pay off the defendant’s personal debts.

Defending barrister Nicholas Mason said the case had been hanging over Thornton for more than two years, had put a strain on his marriage, and he would find custody a harrowing experience.

A specialist financial investigation into his affairs will now take place.