Yorkshire police had Tube bomber's fingerprints years before 7/7

West Yorkshire Police admitted yesterday that it had only last month found two sets of Mohammad Sidique Khan's prints in its archives. It is understood that the prints, which were taken in 1986 and 1993, were not discovered earlier because of a spelling mix-up in the files.

Police chiefs have begun an inquiry into the affair, which may lead to fresh questions about whether the attacks could have been prevented.

Khan, 30, from Dewsbury, led the suicide bombing campaign which killed 52 innocent people in London on July 7, 2005. He had come to the attention of police and MI5 several times before the attacks, particularly when security services investigated a fertiliser bomb plot.

West Yorkshire Police had even photographed him at a suspected terror training camp in the UK in 2001.

The fingerprint records came to light on March 11 when Scotland Yard asked West Yorkshire officers to trawl through their archives in preparation for the July 7 inquests, which are expected to start in October.

West Yorkshire Police took Khan's prints for the first time when he was arrested in April 1986, aged 11, for receiving stolen goods. The prints had been filed under the name "Mohammed Sidique Khan".

A second set of prints, filed under the name "Sidique Khan", were taken in February 1993, when he was arrested on suspicion of assault occasioning actual bodily harm.

Details of the discovery emerged at a hearing at the Royal Courts of Justice in London to decide what form the inquests should take.

A spokesman for West Yorkshire Police said: "Having found this information, West Yorkshire Police considered it appropriate to disclose it to the coroner to the inquests.

"West Yorkshire Police are making inquiries into these records and continuing preparations for the forthcoming inquests."

Max Hill QC, counsel for the Metropolitan Police, stressed that this was not the first time that Scotland Yard asked West Yorkshire Police for detailed information about Khan.

The Met first asked for Khan's fingerprints on July 10, 2005, but West Yorkshire Police told them a day later they did not exist.

A Scotland Yard spokesman said: "In our role assisting the coroner in gathering any information or evidence which may be needed for the hearings the Metropolitan Police Service has liaised with a number of parties in recent weeks, including West Yorkshire Police, who we asked to check and confirm that the position they set out in 2005 was accurate."

Khan carried out the attacks with fellow suicide bombers Jermaine Lindsay, who grew up in Huddersfield, and Shehzad Tanweer and Hasib Hussain, from Leeds.

The coroner, Lady Justice Hallett, must decide whether their inquests should be combined with those for the 52 innocent victims. Relatives of those killed oppose the hearings being held together.

Lawyers for many of the families say the inquests should include a broad-ranging investigation of whether the authorities could have prevented the bombings.

However, MI5 argues this is both unnecessary and impossible because such an inquiry would require the disclosure of intelligence files which must remain secret to protect national security.

The pre-inquest hearing resumes today.