PC Blakelock's son Kevin says those responsible for his father's murder have nowhere to hide.
He said: “People who do horrific acts like this, should not be able to sleep well at night. They should always have a thought in their mind that justice will be served one day and the knock will come on the door.”
The family hope despite the passage of time that this new appeal for information will help to push the investigation forward. Anyone with information can contact Crimestoppers on 0800 555 111 or theMetropolitan Police Incident Room - 020 8203 4617.
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The pair, believed to be the boy's mother and stepfather, were held after the five-year-old's lifeless body was discovered in a lagoon.