Retired Christopher Tappin is travelling to Texas to face charges over his involvement in the export of Hawk surface-to-air missiles to Iran between 2005 and 2007.

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65-year-old Mr Tappin arrived at the custody suite at Heathrow Airport on Friday morning. He was introduced to two US marshalls, placed in leg irons and flown to El Paso, Texas. It is a far cry from the plush Kent home in Orpington where Channel 4 News interviewed him 48 hours ago.

With his wife by his side, Chris Tappin explained that the Americans want him because between 2005 and 2007 he was involved in the export of what turned out to be batteries for Iranian surface to air missile systems. The company he was trading with, MGE, turned out to be the FBI. It was a sting.

Mr Tappin said he did not know that the batteries were meant for military hardware and that the onus was on the exporter in America to obtain the relevant export licences.

Power imbalance

The case again throws into the focus what critics claim is the lopsided nature of the extradition treaty between the America and the UK.

According to the treaty, when UK authorities want an American they have to hand over "such information as would provide a reasonable basis to believe that the person sought committed the offence".

When the Americans, on the other hand, want a British citizen, they do not have to provide this information. A recent government review concluded that the system was fair, that the disparity reflected the differences in both countries' legal systems rather than judicial power imbalance.

In a answer to parliamentary question on Thursday, the prime minister said that the Home Secretary Theresa May was examining the findings of a recent review of the treaty and that she would "take into account the views of parliament that have been expressed in recent debates".

He appeared to be raising the prospect that fundamental reform may yet be on the agenda.

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