By Danny Savage
BBC North of England Correspondent
Mr Lawrence describes life without his daughter
The disappearance of Claudia Lawrence has occupied the minds of her family and the time of North Yorkshire Police for six months now.
How could a well-liked 35-year-old with apparently everything to live for just disappear?
Her father, Peter Lawrence, has campaigned tirelessly to keep the profile of his daughter's disappearance in the public eye. He remains optimistic that he will eventually get an answer.
"I firmly believe that someone, be it a relative, a workmate or a neighbour does know something or has seen somebody acting strangely," he said.
"They may not have thought it important but everything is important. Leave the police or Crimestoppers to judge that.
"Somebody has that vital piece of information and in other investigations it has sometimes taken quite a long time for it to come out".
Claudia was last seen alive close to her home on Heworth Road in York on the afternoon of 18 March.
Detectives have always worked on the assumption that she left home very early the following morning to walk the one-and-a-half miles to work at York University. But she never arrived at work.
Appeals on the BBC Crimewatch programme have focused on a couple seen along the route talking to each other and a man and a woman seen arguing close to the entrance of the university that morning. Was Claudia the woman?
For the first few weeks the search for her was high profile.
Uniformed officers searched woodland, divers went through streams and rivers.
Even all the manhole covers close to her home were lifted in the hunt for clues. But six months on there appears to be no firm lead in the inquiry.
Six weeks after she vanished police reclassified the investigation as a suspected murder inquiry, although they admit they have no evidence she is dead.
Miss Lawrence's disappearance is being treated as suspected murder
There has been speculation about Claudia's personal life. She did have boyfriends who her family and friends knew nothing about and her personal life may well be the answer to this mystery.
Peter Lawrence says the last six months have taken their toll.
"One day, hopefully soon, we will get an answer to this.
"You feel it going for a walk in the countryside or sitting at home. You just have a sinking feeling.
"I hope it's the answer we want but it's the not knowing which is the worst part of this. That's what eats into you."
He tries to keep himself busy by continuing to work from home as a solicitor and campaigning for help in finding Claudia.
He has high-profile support too. The Archbishop of York, John Sentamu, has been seen at his side handing out leaflets in the city where Claudia disappeared - a city which is widely regarded as a safe place to live.
But until the riddle of Claudia Lawrence's disappearance is solved people will understandably question that reputation.
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