2. The assassination of John F Kennedy

JFK was shot on Friday, November 22, 1963, in Dallas, Texas at 12.30pm . He was fatally wounded by gunshots while riding with his wife - Jacqueline Kennedy - in a motorcade. The ten-month investigation of the Warren Commission of 1963 to 1964, the United States House Select Committee on Assassinations (HSCA) of 1976 to 1979, and other government investigations concluded that the President had been assassinated by Lee Harvey Oswald - who was himself shot dead by Jack Ruby while in police custody.

But doubts about the official explanation and the conclusion that Oswald was the lone gunman firing from the Texas Book Depository overlooking Dealey Plaza where Kennedy was hit surfaced soon after the commission report. Footage of the motorcade taken by Abraham Zapruder on 8mm film supported the growing belief that at least four shots were fired - not the three that the Warren Commission claimed. The moments of impact recorded on the film also suggested that at least one of the shots came from a completely different direction to those supposedly fired by Oswald - evidence backed up by testimony of several eye witnesses. Many believed that several shots were fired by gunmen hiding behind a picket fence on a grassy knoll overlooking the plaza.

In 1979, the House Select Committee on Assassinations (HSCA) found both the original FBI investigation and the Warren Commission Report to be seriously flawed. The HSCA also concluded that there were at least four shots fired and that it was probable that a conspiracy existed. However, later studies, including one by the National Academy of Sciences, have called into question the accuracy of the evidence used by the HSCA to support its finding of four shots.

3. Roswell

The event that kick-started more than a half century of conspiracy theories surrounding unidentified flying objects (UFOs). Something did crash at Roswell, New Mexico, sometime before July 7, 1947 and - at first - the US authorities stated explicitly that this was a flying saucer or dis. Numerous witnesses reported seeing metallic debris scattered over a wide area and at least one reported seeing a blazing craft crossing the sky shortly before it crashed. In recent years, witnesses have added significant new details, including claims of a large military operation dedicated to recovering alien craft and aliens themselves, at as many as 11 crash sites, and alleged witness intimidation. In 1989, former mortician Glenn Dennis claimed that he was involved in alien autopsies which were carried out at the Roswell air force base.

The conspiracy theory has been fanned by the US military repeatedly changing its story. Within hours of the army telling reporters that it had recovered a crashed saucer, senior officers insisted that the only thing that had fallen from the sky had been a weather balloon. A report by the Office of the Secretary of the Air Force released in 1995, concluded that the reported recovered material in 1947 was likely debris from a secret government program called Project Mogul, which involved high altitude balloons meant to detect sound waves generated by Soviet atom bomb tests and ballistic missiles. A second report, released in 1997, concluded that reports of alien bodies were likely a combination of innocently transformed memories of military accidents involving injured or killed personnel, and the recovery of anthropomorphic dummies in military programs like Project High Dive conducted in the 1950s.

4. Nasa faked the moon landings

Some of the theories surrounding this subject are that the Apollo astronauts did not land on the Moon; Nasa and possibly others intentionally deceived the public into believing the landings did occur by manufacturing, destroying, or tampering with evidence, including photos, telemetry tapes, transmissions, and rock samples; and that Nasa and possibly others continue to actively participate in the conspiracy to this day.

Those who think that Nasa faked some or all of the landings base their theories on photographs from the lunar surface which they claim show camera crosshairs partially behind rocks, a flag planted by Buzz Aldrin moving in a strange way, the lack of stars over the lunar landscape and shadows falling in different direction. Many commentators have published detailed rebuttals to the hoax claims, and these theories have been generally discounted.

5. The Illuminati and the New World Order

A conspiracy in which powerful and secretive groups (the Illuminati, the Bilderberg Group and other shadowy cabals) are plotting to rule mankind with a single world government. Many historical events are said to have been engineered by these groups with one goal - the New World Order (NWO). The groups use political finance, social engineering, mind control, and fear-based propaganda to achieve their aims. Signs of the NWO are said to be the pyramid on the reverse of the Great Seal of the United States, strange and disturbing murals at Denver International Airport, and pentagrams in city plans. International organisations such as the World Bank, the IMF, the European Union, the United Nations, and Nato are listed as founding organisations of the New World Order.

6. Elvis Presley faked his own death

A persistent belief is that "the King" did not die in 1977. Many fans persist in claiming he is still alive, that he went into hiding for various reasons. This claim is allegedly backed up by thousands of so-called sightings. The main reason given in support of the belief that Presley faked his death is that, on his grave, his middle name Aron is spelt as Aaron. But "Aaron" is actually the genuine middle name for Presley. Apparently, either Presley or his parents tried to change the name to "Aron" to make it more similar to Presley's stillborn twin, Jesse Garon Presley.

7. Shakespeare was not Shakespeare

Who really was the English language's greatest writer? Among the numerous alternative candidates that have been proposed Francis Bacon, Christopher Marlowe, William Stanley (6th Earl of Derby) and Edward de Vere (17th Earl of Oxford), are the most popular. Theorists believe there is a lack of evidence proving that the actor and businessman sometimes known as Shaksper of Stratford was responsible for the body of works that bear his name. Very little biographical information exists about Shakespeare.

8. Paul McCartney is dead

“Paul is dead” is an urban legend alleging that Paul McCartney died in a car crash 1966 and was replaced by a look-alike and sound-alike. "Evidence" for McCartney’s death consists of “clues” found among the Beatles’ many recordings. Hundreds have been cited at various times by various people.

They include statements allegedly heard when a song is played backwards, symbolism found in obscure lyrics, and ambiguous imagery on album covers. A few of them are well known, such as the fact that McCartney is the only barefooted Beatle and is out of step with the others on the cover of Abbey Road, pictured.

9. Harold Wilson was a Soviet agent

Soviet defector Anatoliy Golitsyn is thought to have claimed that Wilson was a KGB spy. He further claimed that Hugh Gaitskell was assassinated by the KGB so that he could be replaced as Labour leader by Harold Wilson. Furthermore, former MI5 officer Peter Wright claimed in his memoirs - Spycatcher - that he had been told that Wilson was a Soviet agent. MI5 repeatedly investigated Wilson over the course of several years before conclusively deciding that he had no relationship with the KGB. On the BBC TV programme, The Plot Against Harold Wilson, broadcast in 2006, it was claimed that the military was on the point of launching a coup d'état against Wilson in 1974. Wilson himself told the BBC that he feared he was being undermined by MI5 in the late 1960s after devaluation of sterling and again in 1974 after he narrowly won an election against Edward Heath.

10. The Aids virus was created in a laboratory

Based on the theories of Dr William Campbell Douglass, many believe that that HIV was genetically engineered in 1974 by the World Health Organisation. Dr Douglass believed that it was a cold-blooded attempt to create a killer virus which was then used in a successful experiment in Africa. Others have claimed that it was created by the CIA or the KGB as a means to reduce world population.