Claudia Lawrence: North Yorkshire police chief's regret
One of North Yorkshire's most senior police officers has said the "stand out regret" of his career is failing to solve the disappearance of chef Claudia Lawrence.
Deputy Chief Constable Tim Madgwick said the the mystery around the case will "frustrate me intensely".
Miss Lawrence disappeared on her way to work in York in March 2009. Officers believe she was murdered.
Mr Madgwick is retiring from North Yorkshire Police after 29 years.
Speaking to BBC Radio York, he said: "The stand out regret for me, because I've been heavily involved, is Claudia Lawrence.
"I would dearly love to bring some resolution for the Lawrence family to that case and I know many of my colleagues feel exactly the same.
"When I think about finishing my career that will frustrate me intensely that we haven't been able to resolve that and bring justice to her family.
"It does tend to gnaw at you after a few years, because I think surely we must be able to get there.
"I hope one day the people who follow in our footsteps manage to achieve what we didn't achieve."
In January the force said active investigation of the case was being brought to an end.
Nine individuals have been arrested or interviewed in connection with the case since a review began in 2013, but no charges have been brought. The case remains open.
Mr Madgwick joined North Yorkshire Police in 1988 and rose through the ranks from PC to Deputy Chief Constable and had two stints as Acting Chief Constable.
In 2004 he was part of the team responsible for hunting down killer Mark Hobson, who went on the run after murdering four people.
"It's very strange [to be retiring] I've been involved with some great people and dealt with some really major events," he said.
Lisa Winward has been named as his replacement.