But nothing prepared him for the export transaction that now threatens to separate him permanently from his home and family – himself.
Barring a last-minute intervention by the European Court of Human Rights, the 65-year-old grandfather and president of the Kent County Golf Union will receive a phone call as early as next week asking him to attend a police station. Once there, he will be met by US marshals, manacled and placed on a flight to Texas to face criminal charges. He has no guarantee of bail and, if convicted, potentially faces 35 years in prison.
This bridge-playing elder statesman of the Kentish gin-and-Jag belt, hitherto a successful businessman and pillar of his community, is the latest target of the controversial extradition treaty with America which campaigners last week described as a "stain" on the presumption of innocence in the British justice system.
Critics, including supporters of Gary McKinnon, sought by the Americans on computer-hacking charges, are asking for a forthcoming government review to make amendments, including introducing a rule allowing courts to prevent extradition if most of a crime was committed here.
All of which is likely to come too late for Mr Tappin, 65, who last month exhausted his final legal avenue in Britain when the High Court threw out his appeal against a ruling that he should face charges across the Atlantic for allegedly trying to sell missile parts to Iran.
He is now contemplating the possibility that he will see out his days in a cell in El Paso for a crime that he not only denies committing, but also claims was invented by the US authorities to entrap a foreign citizen.
Sitting in his house near Orpington, south-east London, which he expects to have to sell to pay his legal fees in the US, Mr Tappin, who retired in 2008 from the freighting agency he founded, struggles to contain his disbelief at what he sees as the failure of the British state to protect him from "frivolous" charges.
He told The Independent: "I was all set to enjoy my retirement with my grandson, my family and playing a bit of golf. And then suddenly this nightmare scenario turns up and I find I have no rights at all in this country.
"No prima facie case has been produced against me by the Americans. The judiciary and the Government have allowed this lop-sided extradition law to be established. Ridiculous."
A dignified man proud of the company he built up from nothing, Mr Tappin will leave behind his five-year-old grandson and his 62-year-old wife, Elaine, who suffers from Churg-Strauss system, a rare auto-immune disorder.
At the heart of the entrepreneur's predicament is a transatlantic customs investigation that seemed to owe more to the pages of an airport thriller than the reality of the West's attempts to hinder Iran's acquisition of weaponry.
Using a Texas-based front company called Mercury Global Enterprises (MGE), agents from US Immigration and Customs Enforcement (ICE) offered Robert Gibson, a Cyprus-based business associate of Mr Tappin, a deal in 2006 to sell five specialised Eagle Pitcher batteries for a total of $25,000 (£16,000).
The criminal complaint filed against Mr Tappin, who is accused of fraud and conspiracy to export military equipment without a licence, alleges he was at the core of an attempt to send the power packs to Tehran in the knowledge that they were a component of US-built Hawk missiles. Washington sold the air defence system to the Shah, leaving Iran's Islamic rulers to seek spare parts on the black market after he was deposed in 1979.
Mr Tappin insists that Mr Gibson, who was subsequently arrested in the US and gave evidence against the Briton in return for a reduced two-year prison term, told him the batteries were for use in car manufacturing and destined for the Netherlands. The word "Iran" was never mentioned.
The entrepreneur also claims he was never given a full description of the batteries by MGE, was lied to about the legal requirements he faced and assured by the "company" that it would obtain the necessary export licences under rules known as "Free On Board", which make the exporter responsible for complying with US regulations.
The result, according to Mr Tappin and his lawyers, is an entrapment operation which would have been illegal under British law and thus renders extradition unthinkable. A legal document filed on his behalf states: "Ultimately, the US agents told lies in order to entrap a respected British businessman."
Certainly, there are question marks over the American case, which ICE claims is bolstered by email traffic proving a conspiracy between Mr Tappin and Mr Gibson. Among the allegations is that Mr Tappin used a false identity, "Ian Pullen", to negotiate with MGE. Mr Pullen is a real person who worked as an import manager for Brooklands.
But, under the rules of the extradition agreement, according to Mr Tappin and his lawyers, none of this can be tested until he finds himself before a US court. Mr Tappin says none of the six witnesses he has lined up to clear his name are yet willing to travel to America to testify, leaving him with the choice of either pleading his innocence without evidence or accepting a plea bargain.
The Briton will hear in the coming days whether an application for his case to be heard in Europe under human rights legislation has been granted.
Mrs Tappin said: "With extradition, you are punished twice. Though you've not been found guilty of anything, you are taken away from your country, your family and your life. It's almost as if you're guilty before you've even got there to defend yourself."
Unequal Treaty: UK-US extraditions
The NatWest Three
The extradition in 2006 of three British bankers – Giles Darby, David Bermingham and Gary Mulgrew – became a cause célèbre after authorities in Texas brought wire fraud charges against them linked to the collapsed energy firm Enron. They struck a plea bargain and were sentenced to 37 months in prison.
Alex Stone
The Briton was extradited to Missouri in 2004 and spent six months in jail awaiting trial on child abuse allegations until the charges were dropped. He criticised the replacement of the requirement on the US authorities to provide a prima facie case with a much lower test of "reasonable suspicion".
Babar Ahmad
The IT worker has been held without trial in Britain since 2004 awaiting extradition for alleged fund-raising for terrorism. His case is currently before the European Court of Human Rights.
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