When Nigel Gallimore, a 41-year-old window cleaner from Dorset, witnessed a light-aircraft crash in August 2004, he didn't hesitate. With no thought for his own safety, he dragged two survivors to safety and sheltered them as the wreckage exploded, an act of courage that netted him the Queen's Commendation for Bravery. Except that it never actually happened. Gallimore was exposed at an inquest last week and the credit given to the real hero of the hour, Mike Winstanley, a 52-year-old window fitter.
It has not been a good week for liars. On Wednesday a 39-year-old plumber from Devon was jailed for three months for lying to police about losing a teenage daughter in the Boxing Day tsunami. Philip Bosson constructed an elaborate story about the death of his non-existent daughter, a lie that eventually cost the local force £6,000 in wasted police time.
On Thursday Hwang Woo-Suk, the South Korean scientist whose extraordinary achievements in the field of stem cell research promised to open up a range of cures, apologised after much of his research was revealed to be faked. And mid-week, the publishers of James Frey's best-selling memoir of alcohol and drug abuse, A Million Little Pieces, offered a refund to readers after it was claimed that sections were invented or embellished.
Stories such as these, which surface with alarming regularity, seem to suggest that the Walter Mitty syndrome - named after the character of a compulsive fantasist created by American writer and cartoonist James Thurber - is frighteningly widespread.
"The desire to want to be somebody important without expending any effort, or making up stories to get attention is actually fairly common," says Dr Colin Gill, a psychologist and expert on the nature of identity. "Of course, we only hear of high-profile cases such as these, when people get caught out. I suspect there may well be thousands of people telling these kind of lies or leading double lives."
In addition to Walter Mitty, the other great anti-hero of self-reinvention is Patricia Highsmith's Tom Ripley. In The Talented Mr Ripley, the character murders and then takes over the identity of his friend, Dickie Greenleaf. At one point Ripley says that surely it's better to be a fake somebody than a real nobody - a line that articulates the sense of inadequacy that festers inside many of these fantasists.
Duncan Roy - the illegitimate son of a Kent cleaner - transformed himself into the aristocratic son of Lady Clare Rendlesham in an effort to escape his background. "As Anthony Rendlesham, I didn't have to clutter my head with all the stories of my family, the terrible times," says Roy, who was imprisoned for credit card fraud and whose story was made into the film AKA. "I could be clean, simple, grand. I was everything I wanted to be ... It was so much better than the life I'd had before."
"There is a suggestion that these kind of fantasies reflect some kind of deficit in childhood - they were not noticed, rewarded or loved - and so, later in life, they go on to try and seek the attention or praise that was denied to them," says Dr Gill. "There is also some evidence to show that this tendency could be genetic and it does seem that Jeffrey Archer inherited some of his talent for invention from his father, who was a bit of a crook and a conman."
This pathological urge to create oneself anew is far from a recent phenomenon. The 19th-century bricklayer Harry Stokes was only unmasked as a woman after his death. In the 1890s, valet Louis Grin masqueraded as the exotically-named Louis de Rougement, an adventurer who lived with the cannibals of Australia for 30 years. And hospital orderly Ferdinand Waldo Demara took over the identity of a doctor, Joseph Cyr, during the Korean War; his story was made into the 1961 film starring Tony Curtis, The Great Impostor.
Yet there is something particularly modern about the desire to erase one's personality with the ease with which a snake sheds its skin. Indeed, it does seem that, at times, we are living in a society that celebrates deception. This week Big Brother awarded celebrity status to Chantelle Houghton, a Paris Hilton lookalike from Essex. Channel 4's Faking It encourages participants to slip on another life. The internet chatroom offers individuals the chance to change their age, gender and background at will, while, in the words of New York Times commentator Frank Rich, the "metamorphoses promised by plastic surgery" now outnumber Baskin-Robbins flavours.
"Not so many years ago positions such as being captain of the local golf club or secretary of the amateur dramatics society automatically gave you a position of authority within your community," says Dr Gill. "Now it's much harder to earn this kind of status. No wonder people take extreme measures to grab a bit of attention for themselves."
In most cases a little toying around with one's identity is harmless, and besides, lying is an integral part of normal, everyday communication. One study from the University of Massachusetts showed that people on average told three lies in every 10 minutes of conversation. Another research project, from the University of Virginia, revealed that men and women lie in a fifth of their social exchanges that last 10 minutes or more, while in a single week individuals deceive nearly a third of people they speak to during one-on-one chats.
Most of us engage in what Dr Gill calls "Impression Management", the editing and manipulation of one's image or expertise. Who hasn't tweaked a CV to present oneself in a better light or stolen other people's funny stories and told them as one's own? "This kind of behaviour is totally normal and it only becomes a problem when the lies get out of hand and reach the level where it is compulsive," says Dr Gill.
Can't we all relate to the way this happens? A person, perhaps not used to getting much attention, suddenly as a result of telling a lie finds him or herself basking in the limelight. So they tell another lie, which in turn makes them feel better about themselves; and so the process continues until they have become addicted to, and adept at, deception.
Yet even though we might relate to it, few of us would go so far. At this end of the spectrum people who lie probably are suffering from personality disorders - definable psychiatric conditions linked to childhood experiences and, it is increasingly thought, to brain structure. A recent study in the British Journal of Psychiatry showed that people who habitually lie, cheat and manipulate others have more pre-frontal "white matter" and slightly less pre-frontal "grey matter" than non-liars. This extra white matter, the basic wiring in the brain, could provide liars with the tools necessary for them to manipulate and deceive.
"Our argument is that the more networking there is in the prefrontal cortex, the more the person has an upper hand in lying," says Adrian Raine, co-author of the study and psychology professor at the University of Southern California. "It's almost mind-reading - you have to be able to understand the mindset of the other person. You also have to suppress your emotions or regulate them because you don't want to appear nervous. Their verbal skills are higher. They've almost got a natural advantage. They've got the equipment to lie, and they don't have the disinhibition the rest of us have in telling the big whoppers."
Andrew Wilson is the author of 'Beautiful Shadow: A Life of Patricia Highsmith' (Bloomsbury) and a forthcoming novel 'The Lying Tongue' (Canongate)
The lying game: the men who fooled the world
FRANK ABAGNALE: He was the ultimate serial conman. For five years, Abagnale posed as an airline pilot, a doctor and a lawyer, in the process defrauding banks of $2m (£1.1m ) - all before he had turned 21. Famous for using his bogus status and natural charm to seduce women, he slipped through law enforcers' fingers several times before he was caught and jailed for five years. But the legend lives on: his antics were immortalised in the 2002 Steven Spielberg film Catch Me If You Can.
DAVID HAMPTON: It was while trying to gain entry to the New York nightclub Studio 54 that Hampton thought up the ruse that would lead to a lifetime of infamy and the film Six Degrees of Separation: he posed as the son of the actor Sidney Poitier, and was swiftly ushered into the club. Hampton went on to adopt the persona across New York and conned dozens of wealthy Manhattanites out of thousands of dollars. In 1983 he was convicted of fraud, forced to repay the money and banned from entering New York City. He was later jailed after failing to comply, and died in 1993.
LORD BUCKINGHAM: During a routine passport inspection at Calais last year, it emerged that Lord Buckingham, the man standing before officials, did not exist. Using the same method as the killer in the novel The Day of the Jackal, he had stolen the identity of a baby: Christopher Edward Buckingham, who had died in 1963. When he was arrested, he continued to insist he was Lord Buckingham despite overwhelming evidence of his fraudulence, and he has since continued to refuse to reveal his true identity. He used the false one for over two decades, and even his ex-wife and two children do not know his real name. Last November he was jailed for 21 months.
BRIAN MACKINNON: For two years, MacKinnon, 32, managed to dupe pupils and teachers at his old school into believing that he was 17-year-old Brandon Lee. He adopted a Canadian accent and forged two letters to apply for a place at Bearsden Academy, in Glasgow, where he had studied 13 years earlier. MacKinnon excelled academically and started a degree in medicine at the University of Dundee - his ambition all along. His duplicity was uncovered when his passport came to light during a holiday in Tenerife with three girls from Bearsden.
JOHN STONEHOUSE: It took months of preparation, a dead man's passport and a pile of his clothes abandoned on Miami beach for John Stonehouse to convince the world in November 1974 that he had drowned. But the Labour MP and former minister had in fact fled to a new life in Australia with his secretary, leaving behind a string of collapsed and fraudulent companies. He was caught and extradited to Britain in 1975, then jailed for seven years.
ROBERT HENDY-FREEGARD: A former barman and car salesman who reinvented himself as an MI5 spy, Hendy-Freegard began a decade of deception in 1992 when he told a group of friends they were being targeted by the IRA. His eight victims were given a series of bizarre missions, subjected to years of poverty in "safe houses" and conned out of more than £600,000. Several of his female victims had relationships with him, and one even had two children by him. Tried last year, he is serving a life sentence.