Claudia Lawrence went missing in March 2009 after failing to arrive at her job at the University of York.
She was reported missing two days later by her father Peter, who died earlier this year, aged 74, without ever finding out what happened to his beloved daughter.
So who was Claudia and what is known about her last movements?
Claudia, who was 35 and single, worked as a chef at the university’s Goodricke College.
She was due to start work at 6am on Thursday 19 March but failed to arrive after a three mile walk from home.
Forensic evidence suggested she ate her breakfast and brushed her teeth on the Thursday morning.
Her chef’s uniform, her silver Samsung D900 mobile phone and a blue and grey Karrimor rucksack she is thought to have been carrying have never been found.
She was last seen alive at 3.05pm the previous day as she walked home.
But she spoke to her father and to her mother, Joan, on the phone on the Wednesday evening and was reportedly in a good mood.
Her bank account has remained untouched ever since and there is no suggestion Claudia upped sticks and moved to another part of the country or the world. Detectives are convinced she was killed.
In the intervening 12 years there have been numerous theories about what became of Claudia.
Nine people have been arrested, questioned and then released without charge.
Among the clues the detectives have focused on are a left-handed smoker who was seen with a woman on Melrosegate bridge in York around 5.35am on the morning of 19 March.
A man and woman were also seen arguing outside the university at about 6.10am.
A cigarette butt was also found in Claudia’s car and had traces of male DNA on it. The individual who smoked it has never been identified.
Claudia’s phone was switched off at around midday on 19 March, although it is not clear if that could have been because her battery died.
Police have also been baffled by the disappearance of Claudia’s hair straighteners, which she rarely took out of the house.
The Yorkshire Post reported that police initially thought she may have left of her own accord and may have moved to Cyprus, where she had visited and had friends.
It has also been speculated she became the prey of a serial killer who she happened to come across on her way to work. Stephen Fulcher, the detective who caught Wiltshire killer Christopher Halliwell suggested he may have been responsible, despite the lack of solid evidence.
But the most likely explanation is that she was engaged in a secret relationship - which her friends and family were not aware of - which turned sour.
North Yorkshire Police searching for the body of Claudia Lawrence
© Photo : North Yorkshire Police
On Tuesday, 24 August, the police began searching the gravel pits at Sand Hutton, which are nowadays filled with water and are a popular spot for fishing.
Mrs Lawrence told the BBC she was "very, very churned up" about the new search. She said since her daughter vanished "every single day is a nightmare.”
Superintendent Wayne Fox, who is leading the investigation, said: "I cannot say exactly how long these searches may take, however, it is likely that specialist officers and staff, including underwater search teams and forensic experts, will be here for a number of days."
"While I am unable to disclose what has led us to this area, I must stress that the searches are just one of several active lines of enquiry currently being pursued…in our efforts to establish what happened to Claudia and identify any person responsible for causing her harm."