KILLER David Roustoby believed police had enough evidence in 2007 to arrest him on suspicion of murder.

He had told police he had been with David Clarke in the hours before he died, making him the last person to see him alive - and Mr Clarke had told them how Roustoby had held a gun to his head some months earlier. Roustoby also had several previous convictions for violence.

But a months-long investigation into the death led to an open verdict at an inquest and the police turned their attention to other matters.

A North Yorkshire Police spokesperson said: “We wholeheartedly recognise that there may have been some shortfalls in the investigation in 2007.”

There were several indications that year that Mr Clarke had not died by accident or by his own hand at Towthorpe Bridge.

A 2007 postmortem revealed he was drunk and had diazepam in his body, a prescription he had told his doctor he would never take. To walk to the bridge, he would have had to navigate 4.6 miles from his home when intoxicated, including crossing the Outer Ring Road and possibly negotiating the final stretch in the dark without street lighting.

There was no torch with him, no car parked nearby but there were tyre marks indicating a car had pulled up sharply at the layby by the bridge.

So how did he get to Towthorpe Bridge and why?

His body was lying in a strange position for someone who had fallen or who had jumped.

If he had wanted to commit suicide by drowning, he could have jumped into the River Foss from his back garden.

Two days after Mr Clarke died, Sharron Roustoby rang police to say her Fiesta had been stolen and David Roustoby would deal with police inquiries.

The burnt out car was found shortly afterwards, with marks on the driver’s door that could have been made by a thief.

But it had a security microchip that prevented it being started without the right key - and David Roustoby had previous convictions for stealing and torching a car in 1997.

Mr Justice Goss, the judge in the case, said nothing about the 2007 police investigation. But he did praise the 2020 police team that finally brought David Roustoby to justice.

North Yorkshire Police today said it was investigating why its 2007 inquiry into David Clarke’s death wasn’t a murder hunt.

A spokesman said it was looking into the circumstances that led to the open verdict at the 2008 inquest.

“As soon as new information came to light in connection with David Clarke’s death, detectives have worked tirelessly to ensure a rigorous investigation, in order to bring the case to where it is today.

“North Yorkshire Police continues to improve its training around investigative standards, and encourages supervisor scrutiny throughout every step of an investigation.”

The 2020 senior investigating officer, Detective Inspector Nichola Holden said as David Roustoby started a life sentence: “It is a testament to the hard work and commitment of the investigation team that Roustoby was put before the courts so long after the murder, leaving nothing untouched and an exemplary investigation throughout."