Facing extradition to the United States under a controversial new British law, the 40-year-old Scot's miserable plight seems as unlikely as the script for the hit 1983 film.

Prosecutors paint McKinnon as a super-hacker who broke into US defence computers, sabotaged systems and stole secret information that might have been 'useful to an enemy'. Not long after the September 11 terrorist attacks, they say he rendered critical systems inoperable, causing US$700,000 worth of damage.

His mission: to 'influence and affect the US government by intimidation and coercion'.

If true, the location for McKinnon's unsettling online forays - a bedroom in his girlfriend's aunt's house in suburban north London - would certainly give hope to other hi-tech geeks plotting America's downfall.

He doesn't deny snooping on military servers, albeit from a painfully slow dial-up connection. McKinnon describes himself as a 'bumbling computer nerd' who was simply looking for evidence of UFOs. His vagueness on exactly what he uncovered is probably because he was 'smoking too much dope'.

So, evil terrorist or hapless hacker? It's a question that now seems destined to be argued in an American court, after British Home Secretary John Reid approved the extradition.

Not surprisingly, McKinnon - who has given few interviews since his arrest in 2002 - is horrified by the prospect of serving time across the Atlantic.

'I'm sitting up all night thinking about jail, ' he told one reporter last year. 'It is absolutely terrifying. Especially because a friend of mine was on holiday in America once and was viciously attacked and ended up killing the guy who attacked him. He did 10 years in an American prison. He's quite a tough guy, and he said he had to fight tooth and nail every single day, not let up at all. And I'm thinking, 'I'm only a little nerd'.'

The chain-smoking hacker got his first computer when he was 14 and left his job as a hairdresser to do an IT degree at university, which he failed.

Despite the setback, McKinnon found work in the computing industry.

The hacking began in 1995 and soon developed into an obsession as McKinnon scoured the internet looking for holes in US government and military networks. 'I'd stopped washing at one point,' he told the BBC. 'I wasn't looking after myself. I wasn't eating properly. I was sitting around the house in my dressing gown, doing this all night.'

His tactics appear to have been unsettlingly simple. With the help of commercially available software he located machines using the Windows operating system that had no password or firewall protection. Supporters accuse US authorities of making him a scapegoat to disguise shortcomings in supposedly secure facilities.

McKinnon says he noticed a number of other hackers all over the world snooping on the same systems at the same time as him. Last year there were a reported 160,000 hacking attempts on Pentagon computer networks, many of them successful, and cyber attacks continue to be a huge security issue for the US government and military.

'Numerous states, terrorist and hackers groups, criminal syndicates, and individuals continue to pose a threat to our computer systems,' Defence Intelligence Agency director Major General Michael Maples told the US Congress last year.

But the bid to extradite an alleged cyber-criminal like McKinnon is highly unusual.

The painfully slow pace of extradition cases partly explains the paucity of hackers sent to America, but the controversial 2003 Extradition Act imposed in Britain without parliamentary approval has paved the way for McKinnon's departure.

The treaty with the US was primarily intended to fast-track the extradition of terror suspects, but more than half of the 49 Britons singled out so far by the American authorities are accused of white-collar crimes.

Arguably the most high-profile of those are the so-called 'NatWest Three', who last Thursday were flown to the States to face trial in Texas.

Bankers David Bermingham, Giles Darby and Gary Mulgrew deny pocketing millions of dollars in a fraud involving the collapsed American energy giant, Enron. And for three years they campaigned to face justice in the UK.

Just 24 hours before they left Britain, one of their former colleagues, Neil Coulbeck, was found dead in a London park after apparently taking his own life. He was understood to have been a defence witness in the case.

While American senators have yet to ratify the treaty, moves are afoot in Britain's House of Lords to overturn a law that abolished the requirement of US prosecutors to produce evidence of guilt in extradition cases. In cases going in the opposite direction, British authorities still have to prove 'probable cause'.

'This is a double embarrassment for our country, and it works against our national interest,' said Sir Menzies Campbell, leader of Britain's third-largest political party, the Liberal Democrats.

'My argument is not with the United States. Its government is looking after the interests of its citizens. I only wish the UK government would do the same for us.'

Lawyers for McKinnon - who is appealing against his extradition - have argued he could be sent to Guantanamo Bay as a terror suspect.

His case bears similarities to another Briton arrested in 1997 for hacking into US military computers.

Matthew Bevan was labelled by US authorities as 'the single biggest threat to world security since Adolf Hitler', but extradition attempts failed and the case collapsed.

The US government appears to view McKinnon just as seriously. Prosecutors say that between February 2001 and March 2002 he hacked into dozens of US army, navy, air force, and Defence Department computers, as well as 16 Nasa computers, sabotaging systems and causing hundreds of thousands of dollars of damage.

McKinnon regrets the snooping but denies he acted with malicious intent.

Just like Bevan, he maintains he was hunting for evidence of UFOs and says he made some interesting discoveries.

Lists of 'non-terrestrial officers' and ships that didn't correspond to anything in the US air force or navy led him to suspect the existence of a secret space station and fleet.

He believes the US government has reverse engineered an anti-gravity propulsion system from recovered alien spacecraft.

To some observers these are the rantings of a delusional fantasist whose sloppy and amateurish hacking techniques got him caught.

But most agree they are not the actions of someone who deserves to be extradited and sent to jail for the rest of his life.