THE Heather Barnett inquiry was the most extensive, complex and sustained investigation ever carried out by Dorset Police.

Officers scoured the globe seeking new experts and forensic tests for a breakthrough.

They reignited a shelved missing persons inquiry in Italy and appeared on Crimewatch twice and its Italian counterpart.

The force mounted a sustained surveillance operation for years on prime suspect Danilo Restivo that never wavered until he was charged.

The Major Crime and Investigation Team’s investigation lasted nine and a half years and cost millions of pounds.

During this time police collected 700 plus statements, 6,200 exhibits and amassed 7,300 documents.

The investigation was first led by Detective Supt Phil James between 2002 and when he retired in 2007 and then handed over to Detective Supt Mark Cooper, who had been Mr James’ deputy since the beginning of the investigation.

Mr Cooper said he was constantly under pressure to prove he was taking the case forward and the resources being thrown at the investigation were necessary.

Restivo became a suspect in the case from day one – although was not initially the main suspect. Heather’s ex-partner David Marsh was top of the list at first.

Police intelligence, coupled with Heather’s concerns about his visit to her home and the loss of her house key fuelled suspicions about the Italian.

Other key areas for detectives were the discovery of his Nike trainers smelling of bleach the day after they inquired about them. His alibi also didn’t add up.

Convinced Restivo was their man, the police put him under constant surveillance at the end of 2003.

He was watched at his home and out and about in town and his home and car had been bugged.

In spring 2004 they saw him making repeated trips to the Throop Mill and Pig Shoot Lane areas.

Restivo under surveillance in 2004

His behaviour on May 12 was so worrying detectives were forced to send uniform police officers to search his car.

They found a change of clothes, a knife and tissues in a bag, a jacket with a balaclava and gloves inside and two pairs of scissors.

Det Supt Cooper said: “I can honestly say we prevented something that day.”

During 2004 the Heather Barnett murder inquiry team publicly revealed significant new leads in the investigation including a link between Heather’s murder and the disappearance in Potenza, Italy, of Elisa Claps.

They also appealed for women who had their hair cut on buses in Bournemouth since 2002 to step forward.

And on June 22, 2004, detectives arrested Restivo on suspicion of Heather’s murder but he was later released on bail.

The team of detectives working on the murder case made repeated visits to Italy to look into Elisa’s disappearance and incidents of hair cutting on buses there.

It has been widely reported that there were a number of failings in the Italian investigation into Elisa’s disappearance.

Clothes Restivo was wearing on the day Elisa disappeared were not seized.

And the church was not fully searched – had it been so they would have immediately discovered her body.

Det Supt Cooper said: “If they had fully searched the building, Heather would still be alive.”

In a bid to crack the case Phil James made two appeals on BBC1’s Crimewatch before appearing on the Italian version of the crime fighting programme.

In November 2006 Restivo was arrested in connection with hair cutting incidents in Bournemouth but later released.

In August 2008 a dedicated team was set up to look at the inquiry and that October Det Supt Cooper received the news he had been waiting for – new tests on a green towel found in Heather’s home contained the partial DNA profile of Restivo of 1 in 57,000.

They also received further forensic information that traces of blood were found inside the trainers seized from Restivo’s home.

While officers began compiling their case against Restivo, a massive breakthrough came in the inquiry on March 2010.

Elisa Claps’ remains were discovered in the loft of the Trinity church in Potenza.

She had been murdered and sexually assaulted.

He was arrested in Bournemouth on May 19, 2010, and charged with Heather’s murder the following day.