- A huge manhunt began after the model Sally Anne Bowman was found murdered close to her home in South London in September 2005.

Police took DNA from 1,700 men who volunteered for the intelligence-led screening but the investigation went nowhere.

Then, in June 2006, a minor incident was to prove crucial. Mark Dixie, a chef, was arrested after a brawl in the pub where he worked. So minor was it that no further action was taken by police, but his DNA was recorded and loaded on the national database.

Detectives were soon notified that it had produced a good match to the DNA from the murder victim and within five hours he was under arrest. He was charged, convicted and jailed for life, with a minimum term of 34 years.

- Between 1989 and 1996 Anthony de Boise, an architect who worked as a planning officer for Wandsworth Council, would disguise himself as a tramp and attack young girls.

But it was not until September 2006 that he was jailed for 13 years on six counts of indecent assault between those dates.

De Boise, 58, a father of two, escaped detection at the time and may have escaped justice altogether had it not been for his sister accusing him of stealing money from their late father’s estate. It was the first time that he had come to the attention of the police.

Even though the theft charge was dropped, a sample had been taken when he was arrested and it was found to match DNA taken from his victims when it was put into the national database.

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