Mrs Crown was brutally murdered in her bungalow on the outskirts of Wisbech in January 2013, before her body was set on fire. At first, the 86-year-old's death was not believed to have been suspicious.

By the time a post mortem revealed she had been repeatedly stabbed in the chest and neck, the crime scene had become contaminated and forensic evidence lost.

Mrs Crown's body was discovered in her home in Magazine Lane, Wisbech, on January 13, 2013. Detectives have made a number of arrests since then, but no-one has so far been charged with her killing.

Today, on the anniversary of her body being found, police insist the inquiry remains live.

'The investigation work over the last 12 months has concentrated on improved forensic techniques and the re-examination of exhibits,' said a spokesman for Cambridgeshire police.

'This investigation remains an active undetected murder enquiry and anyone with information is asked to contact police on 101 or Crimestoppers, anonymously, on 0800 555 111 or via their online reporting system at www.crimestoppers-uk.org.'

Police and paramedics believed the retired postmistress's death was accidental for the first 48 hours after her body was discovered in her home on Magazine Lane. Officers thought she may have suffered a heart attack after a tea towel caught fire on a cooker.

Coroner William Morris later told an inquest into Mrs Crown's death in March 2012 March that police 'too readily dismissed' foul play or circumstances.'

Despite an appeal on the BBC's Crimewatch programme and re-opening off the investigation with fresh teams of officers, it remains unsolved.

Anyone with information should call police on 101.