Caught by a classic sting, red-faced builder Sean MacMahon paid out tens of thousands to Nigerian fraudsters who asked for his help to transfer millions of dollars out of west Africa.

And the "naive" Tyrone man was then stroked a SECOND time as he tried to claw back his money through another Nigerian conman.

But it is the Ulster Bank that will have to stump up most of the cash lost out in the second swindle to hit Mr MacMahon, after High Court judge Sir Donnell Deeny found it had been negligent in its handling of his banking transfers.

In his judgment, Mr Justice Deeny said Mr MacMahon's problems started when he "left the calm waters of the building trade in Northern Ireland for the choppy seas of Nigerian finance".

The millionaire Cookstown man, the boss of JJ MacMahon Ltd, said he was lured into the swindle after being invited to tender for a building contract at the Nigerian embassy in Dublin.

Although he did not get the job, he said that he had been later approached by a man claiming to be linked to the embassy, who wanted to free up $$9.6m from the Nigerian banking system.

He offered to hand almost $$1m to Mr MacMahon if he helped him.

The judge said Mr MacMahon foolishly agreed and paid over tens of thousands in alleged charges to transfer the money. The builder then went on to pay on similar amounts to "clear" the money through a clearing house in Washington, but still no money appeared.

The desperate Ulsterman eventually approached a contact in South Africa in a bid to claw his money back and was put in touch with another Nigerian businessman, who promised to help him reclaim his money, but instead just ripped him off again!

The man, who the High Court heard has since been jailed on fraud charges in Nigeria, asked Mr MacMahon to transfer a number of cheques for him.

He set up a US dollar account at the Ulster Bank in Cookstown and used it to it transfer over $$50,000 to his new Nigerian contact after receiving a cheque for the same amount.

The businessman did not suspect anything was wrong and accepted another cheque from the Nigerian for $$210,645.

When he sought assurances from the Ulster Bank that it was safe to pay out on the second cheque, Mr Justice Deeny found "that he was told the funds had cleared in early November (2002) with regard to the second inwards cheque".

The judge added: "I find that was not in fact the case and it was therefore a negligent statement by the bank's official. The plaintiff lost as a result."

Mr Justice Deeny said: "I accept the bank would never have opened the dollar account in Cookstown if they had known it was designed to process cheques from Nigeria."

However, he added: "The bank had seemed to have been content to recoup their loss from the plaintiff's company without making any attempt to recover the funds in question or even clarify how the situation had arisen."

Following a court judgment published last week, the bank now faces having to pay back over $$200,000 - plus interest - that had been transferred from Mr MacMahon's personal account to the Nigerian conman in 2002.