Police appeal for letter writer 13 years after mother and five children died in house fire

Police investigating the murder of a mother and her five children in a house fire have appealed to whoever wrote an anonymous letter containing "a number of details" about the incident to come forward.

Abdul Shakoor was the sole survivor of the blaze, which claimed the life of his wife, Sabah Usmani, 44, in Barn Mead in Harlow, Essex, in October 2012. The couple's sons Muneeb, nine, and Rayyan, six, died along with their 12-year-old sister, Hira, soon after the fire.

Their son Sohaib, 11, died in hospital the same day, while their three-year-old daughter, Maheen, died in hospital three days later. Dr Shakoor, who worked at the Princess Alexandra Hospital, had tried desperately to raise the alarm and save his family.

Essex Police are treating the incident as murder, and their investigation, named Operation Shakespeare, has been running for almost 14 years. The force said on Thursday it had received an anonymous letter which sets out "a number of details which we are very keen to progress".

Police said they need to speak to the person directly to be able to do this, and appealed for them to come forward. Appealing for the author of the note to make contact, lead investigator Detective Chief Inspector Louise Metcalfe said whoever wrote it "clearly want(s) Dr Shakoor to get justice for his family.

"The author references the 'nightmare' of having information but not feeling able to share it. Read more on Sky News:Ex-funeral boss admits preventing burialsStorm Dave heads for UKMills sacked after age of alleged victim revealed Detective Chief Inspector Metcalfe told the individual they would "be treated fairly" and reminded them that their information "could be what leads to a person or people being held accountable for tearing the Shakoor family apart".

Detectives are still "committed to securing answers for Dr Shakoor.