POLICE have pledged there will be no let-up in their quest to discover the truth behind the disappearance of university chef Claudia Lawrence.

Four years to the day since she vanished, detectives have promised that one of the biggest and most intensive investigations in the North Yorkshire force’s history will not cease.

Miss Lawrence was 36 when she was last seen at about 3pm on March 18, 2009, after she had walked home from work at York University’s Goodricke College.

Police believe she was murdered - but despite exhaustive efforts which have stretched across the UK and even overseas there has been no trace of her since.

“We have not forgotten Claudia,” said Detective Inspector Adrian Gathercole, the deputy senior investigating officer.

“We have put a tremendous amount of effort into unravelling the events of March 18 and 19, 2009.

“Despite many days of searching by scores of officers and Search and Rescue teams, and a large public response to the enquiry, we have yet to find her. “ He appealed once more for anyone who knows anything about her disappearance to contact police.

“One vital piece of information could make the difference and enable us to complete the picture and finally resolve Claudia’s disappearance,” he said.

“All anniversaries and significant dates magnify the impact of her absence. Our thoughts are with her family as this milestone is reached.”

Police are marking the four years since Miss Lawrence vanished by using Twitter to recall the key times leading up to her disappearance - follow @NYorksPolice and use the hashtag #FindClaudia Miss Lawrence was born in Darlington and brought up in Malton and her family and friends have worked tirelessly to keep her case in the public eye.

Last week a book - Gone, The Disappearance of Claudia Lawrence - was published by writer Neil Root, who worked closely with her family.

The investigation was formerly led by Detective Superintendent Ray Galloway, who retired in January.

He said: “For all of us the investigation became more than a professional function, it was a personal commitment to find out who was responsible for Claudia’s disappearance, and, notwithstanding my retirement, that commitment will sustain.

“The investigation will always remain with me and I am confident that, in the future, a positive resolution will be achieved.”