During the trial, it emerged that clothing and two sticks from the case could not be found and may have been destroyed by Kingston police station property store.

The revelation prompted Judge Georgina Kent to ask for a message to be sent to Kingston police about its evidence storage procedures.

On the witness stand, Detective Sergeant Andrew Morrow, known as Charlie, said it appeared another detective, who took the clothing from three defendants arrested at the scene, had agreed to their destruction earlier this year.

Speaking to the Surrey Comet, he said he found out about the “irritating” destruction only about a month before the case.

Kingston’s borough commander Detective Chief Superintendent Martin Greenslade said: "This was a one-off error. I have no reason to believe it would be repeated."

Officers protecting the mosque during an anti-poppy-burning march had left the building shortly before a threatening mob walked up Richmond Road to attack them.

D Chief Supt Greenslade said the timed withdrawal had been agreed with Kingston Mosque’s management committee.

He said: “When I spoke at the mosque a week later with Edward Davey and Zac Goldsmith, I apologised that we had let the attack happen. With hindsight we would not have left the mosque [until] much later.”

In response to questioning over whether he would allow an anti-Islam or EDL march in Kingston in future, he said it would be considered on its merits, but said: “Better to allow demonstrations than ban one and have a situation like East London Mosque, where people simply turn up and we have no control over what they are going to do.”

Speaking about the convictions of Morris, Pottle and Wallace, he said: “I am delighted. I think it is a result that the mosque and the community can be pleased with.

“Our relationship with the mosque is now so strong it did not need these convictions to cement it further.”

D Chief Supt Greenslade said the investigation was challenging because police were starting with little information and the individuals involved were not known to police.

He said every bit of CCTV needed to be trawled and intelligence gathered from other forces.

He said: “We have outstanding suspects and I appeal to anyone who has any information about them to call us.”

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