Police chiefs today revealed that they are preparing to close Bradford's riot investigation and appealed for help in tracing their last handful of suspects.

The officer heading Operation Wheel - Bradford police's probe into the July 7 disorder - said he was now satisfied that the 'vast majority' of offenders had been rounded up and added that just 12 new suspect mugshots would be released.

Detective Inspector Tony Craven said: "The whole community are keen to know when we will bring this massive investigation to a conclusion.

''We have spent many months trawling through the available evidence and piecing together each offender's involvement. I am satisfied that the vast majority are now in our system and will reach the court stage in the coming weeks and months."

Operation Wheel has been Britain's largest criminal investigation and seen dozens of officers drafted in from their everyday duties.

Det Insp Craven said: "I am asking for the help of the public over the next two weeks with the final 12 photographs.

"We have released 200 photo images of offenders so far and we are now left with a small number to publish to draw Operation Wheel to a close.

"I will then be confident that West Yorkshire Police, on behalf of the community of Bradford, have tried their utmost to put before the courts those responsible for the riot which brought Bradford to its knees."

He added: "We must remind people that during July 7 there was a hardcore of people who committed serious criminal acts.

''This has had a long lasting and damaging effect on the reputation of Bradford and we all have a duty to trace those responsible."

And he added: "More than half of those we have published so far have had the courage to hand themselves in."

So far 233 people have been arrested in connection with the disorder, 195 people charged with a variety of serious offences including 110 people charged with riot, the most serious public order offence in English law.