The disappearance of Claudia Lawrence has baffled detectives for more than 15 years.
Privately educated chef Claudia was 35 when she vanished without a trace after failing to turn up to work at York University on March 19, 2009.
Despite an extensive investigation, there are still key questions that remain unanswered in what has become one of Britains most well-known unsolved murders.
The search for Claudia was launched after her friend grew worried when she did not turn up at her local pub The Nags Head.
Friends informed Claudias father Peter the next day when she still failed to answer any calls. Peter visited her home in the Heworth area of York to find she was nowhere to be seen.
Five weeks after she was reported as a missing person, the case was escalated to a suspected murder investigation - despite her body never being found.
What ensued was a search costing more than £1.5m, with hundreds of officers working to piece together what happened to the chef.
North Yorkshire Police has conducted two investigations and questioned nine people but no charges have ever been brought.
Looking back at the disappearance and evidence found by police in the years following, MailOnline has studied the FIVE overarching questions that still remain.
Claudia Lawrence was 35 when she was reported missing after failing to turn up for work at York University on March 18, 2009
The search for Claudia was launched after her friend grew worried when she did not turn up at her local pub The Nags Head
Who was the mystery man who was spotted outside Claudias home?
The last definite sighting of Claudia had been on March 18, 2009, after she finished work at Goodricke College.
Later that evening, at around 8pm, she spoke to her father on the phone. She then called her mother Joan and the pair watched and spoke about the TV programme Location, Location, Location.
Claudia was said to have sounded normal and relaxed during the call, and had told her mother she was going to sleep early because her car was in the garage and she would need to walk to a work - a 45-minute journey.
The next day she did not turn up to her 6am shift at the university canteen, but when her father forced himself in the next day, it seemed as though she had left for work - her used breakfast plates were in the sink, and her chefs whites, rucksack and mobile phone were all missing.
A man is seen lurking on Heworth Road in York near the home of missing chef Claudia Lawrence on the last night before she failed to turn up to work
A CCTV image shows a man walking down Heworth Place, which leads to the rear of Claudias house, before returning a minute later with a bag over their shoulder
Following her disappearance police searched the inside of her York home for clues
After a thorough search, authorities were unable to find any clues from the property
Following enquiries, police were able to uncover CCTV footage of a man standing behind Claudias house on the morning of her disappearance.
A witness also told police there was a man, aged around 55 to 65, seen standing outside her property at around 6.45am that morning.
While Claudia was understood to be single, she was said to have had several secret relations with men who are thought to have been married or in other relationships.
Images retrieved by police from the same CCTV camera the night before showed what looks to be the same man outside the house. A dark figure can be seen hanging about the area, looking as though he was waiting to meet someone.
The images were timestamped around 7.15pm on March 18 - around an hour before Claudia was on the phone with her parents.
Questions over who the identity of the mystery man has never been confirmed, with detectives still believing establishing his identity could help solve the case.
Claudias father, Peter (pictured together), died in 2021, never knowing what happened to his daughter
Her mother, Joan, continues to hold onto hope that the truth will come out, as she is haunted every day by not knowing what happened to her daughter
Why was there a cigarette butt in her car?
Claudias Vauxhall Corsa was being repaired at a garage at the time of her disappearance.
When police examined the car for clues, they found an Embassy Regal cigarette butt in the ashtray and forensic tests showed that the DNA profile belonged to a male. It was also believed to have come from a left-handed smoker.
Police hoped that running a DNA match could aid them in getting to the bottom of the case. But despite still periodically running checks through the national DNA database, they have never been able to identify the smoker.
Claudia was not a smoker, but it is understood she had no issue with friends and family smoking while in the car.
Senior investigating officer at North Yorkshire Police, Wayne Fox, told The Times earlier this year that all those known to have been in contact with the car assisted the inquiry and are eliminated on the basis of DNA recovery.
Where is her body?
In 2021, a search was carried out at Sand Hutton Gravel Pits, near York. The family were left heartbroken after it found nothing of obvious significance
Police officers outside the home of missing university chef Claudia Lawrence in Heworth, York
Claudia lived by herself at a two-bedroom terraced house in Heworth when she disappeared. But when police attended her house, there was nothing to suggest something had happened to her while in the property.
Police believe that Claudia was murdered, yet her body has never actually been found.
A number of searches were conducted as recently as 2021 but to no avail.
It seemed as though there was a potential breakthrough in the case when specialist teams searched for Claudias remains in the Sand Hutton gravel pits - about eight miles out from York - in August 2021. However, nothing came of this.
Claudias mobile phone - a silver Samsung D900 - and her blue and grey Karrimor rucksack which had her chefs whites were missing when police searched her house, suggesting she had left for work on the morning of March 19.
These items were also never found.
The last message Claudia sent before her disappearance was at 8.23pm on March 18, around the time she was speaking to her parents.
The final text she received was on the same night at 9.12pm from a friend in Cyprus.
Her phone was then deliberately turned off at around 12.10pm on March 19.
Mystery couple arguing outside the university
A motorist reported seeing a man and woman arguing outside the University of York campus at around 6.10am on March 19 - Claudias shift was supposed to start at the universitys Goodricke College at 6am.
The witness told police the couple had been arguing next to a parked car which had the passenger-side door opened.
Just half an hour before, at around 5.35am, a cyclist also reported a sighting of a couple near the electricity substation at Melrosegate bridge, which is on Claudias route to work.
It was said the man had been smoking a cigarette in his left hand, suggesting there could be a link to the cigarette butt found in Claudias car.
Despite several high-profile appeals by the police, the man has never been traced.
The mystery man was described as being 5ft 6in tall, wearing combat trousers and a dark hooded top which covered his face. The woman, who could have been Claudia, was described as being shorter with dark blonde hair, wearing a white t-shirt, overcoat, jeans and white trainers.
It is believed if information were to come forward about the identity of the smoker, it could be a crucial point in solving the case.
Who was in the car behind Claudias house?
In 2014, police released CCTV footage of what they thought could be highly significant in the case.
It showed a vehicle near Claudias house on the morning of March 19.
The video revealed an old-style silver Ford Focus driving along Heworth Road around 5.42am. It was seen braking as it approached Claudias house.
Police also attempted to trace the owner of white Vauxhall Astra which was also caught on CCTV on the evening of March 18.
The car was parked opposite the road from Claudias house, by a Costcutter shop and local chippie, at 9.01pm and remained there for at least 30 minutes.
Detectives tried to track down the owners of the cars, releasing the footage in an appeal for information, but the vehicles were never tracked down.