The police decided to investigate the missing chickens, possibly because it appeared more straightforward rather than finding out who was targeting my daughter, and as a result she was murdered.”

The police failed to devote proper resources to the robbery and beating of Moore even though many clues pointed to Dyche, who had previously been arrested for harassing her and also had a conviction for making death threats against his ex-wife. The force even returned his guns which had been seized after an assault on Moore.

Moore’s case was fully investigated and Dyche’s role in orchestrating it was revealed only after his continued campaign of violence and death threats which resulted in him blasting his former girlfriend to death with a shotgun in March 2004.

Dyche was sentenced to life imprisonment after his conviction in May last year of killing the talented rider, who lived with her mother near Ashbourne.

Until now the shocking lapses by police which allowed Dyche to murder Moore were thought to have been down to incompetence. But the documents show that much of the reason for the failure was because of manpower being diverted to search for the missing chickens.

Last month the Independent Police Complaints Commission (IPCC) announced that six officers had been disciplined, although they were not named in the case.()

Howarth was sacked, Detective Inspector Ian Annable was demoted to sergeant and four others — Detective Chief Inspector Richard Gooch, Sergeant Tracy Lewis, Detective Constable John Birch and Constable Wendy Foxon, were all reprimanded. Gooch was told he had been “close to being demoted”.

It has now emerged that Howarth, Gooch, Birch and Lewis were all involved in a two-month-long inquiry known as Operation Function — the theft of chickens at the Dove Valley processing plant in Ashbourne — at around the time of the attack on Moore in June 2003.

Prosecutor John Beggs wrote in a summary to the disciplinary hearing: “The panel may wish to compare and contrast activity levels in relation to Tania’s robbery with those in relation to Operation Function.”

Beggs wrote that Lewis, Howarth’s supervisor, “was able to manage this operation from April 28 2003] to her departure [to another station] in July 2003, including a ‘strike’ [swoop] on June 20 which involved 40 staff from uniform, CID, taskforce and surveillance”.

Yet at no stage, Beggs said, did she consider discussing the glaring omissions in the baseball bat attack on Moore. Instead, officers’ notebooks were full of references to stolen chickens.

When interviewed by the IPCC team Lewis admitted: “My level of supervision of [the robbery] was probably affected to a degree by my heavy involvement in Operation Function.”

The disciplinary document stated that Birch, brought in to replace Lewis, said that “at least 90% of his handover concerned Operation Function (stealing chickens by employees) and nothing was mentioned to him about the robbery of Tania”.

Police sources said that Operation Function had been considered a “CV job”, meaning it was likely to result in a significant number of convictions, making it an attractive addition to an officer’s record.

Christopher Trafford, then owner of Dove Valley, said this weekend that he had little recollection of the inquiry. “It is nothing unusual for things to go missing in a fresh food factory,” said Trafford, who sold the business in 2004 and is now retired.

“I’m amazed that we have been dragged into something which was the saddest thing that has happened around here.”

His son Nigel Trafford, who was managing director of Dove Valley at the time, said nobody went to jail over the chicken thefts. “It was annoying, it wasn’t going to break us,” he said. “No one went down for it, it was just a number of slapped wrists.”

Derbyshire police, led by David Coleman, chief constable, refused to comment. Howarth, who is appealing against her dismissal, also refused to comment.

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• UK regional accents thrive against the odds
• ‘Scarecrow’ wind farms put rare birds to flight
• What an anti-climax: G-spot is a myth