A FEW nights ago, Ali Simms dreamt she was with her younger sister. It was a dream she wishes more than anything could have been real – because when she woke up, she remembered Claudia Lawrence has not been seen since March 18 last year.

Tomorrow is 500 days since the University of York chef vanished inexplicably without a single clue as to her whereabouts.

Detectives believe she has come to harm after meeting someone she knows, but Ali is now convinced her sister was abducted by a stranger.

She said: “I just think that she must have been. The police have been so thorough in their investigations and invested so much time and money into this that either someone who does know her has covered themselves up fantastically well or it’s a stranger who’s completely off their radar.

“If it is a stranger it becomes like looking for a needle in a haystack and it leaves me with a feeling of not knowing when we are going to get a conclusion to this.”

Ali, 39, who lives in the Peak District of Derbyshire with her husband, Danny, and two sons, Luke, five, and Joshua, one, said the past 17 months had been “awful”.

She said: “It has felt like it’s not real, it still feels like that. I guess at the start there was this element of shock and we just couldn’t believe it had happened. Every day was an absolute nightmare.

“Then, as time has gone on I guess I feel how people must feel if they’ve lost someone, if a member of their family has died and you are missing them.”

But Ali said although she could not help fearing the worst, she still clung to the hope Claudia would be found alive.

She said: “I don’t want to think that, but at the back of my mind there is that element.

“Whenever there is a new search I feel sick because I dread what the news may be, I don’t feel hope that it’s going to be resolved.

“We’ve got a process in place. If it’s bad news, the police will contact my husband first.

“But then if I’m with him and the phone goes and I hear him speaking to the family liaison officer, I immediately feel anxious.

“Although we are living in limbo and it’s awful, I dread to think what the alternatives are. I don’t want to hear bad news.”

Ali said she could not remember details of the dream she had a few nights ago – only that Claudia had been there and everything had been just as it used to be.

“We have led completely different lives, but we chatted regularly,” she said.

“I miss being able to pick up the phone and have a chat. Often it would just be about trivial things, like ‘have you just seen that person on X Factor?’ Ali said occasionally her eldest son would ask whether anybody had found Auntie Claudia yet, but it broke her heart that her youngest son, who was only six months old when his aunt went missing, did not remember her.

She said: “The other day we were watching the documentary that has been produced for Channel Four about Claudia’s disappearance, as they wanted us to see it before it gets shown on television. Joshua was here when it was on and he kept saying ‘granddad on TV, granddad on TV’. Then they would show Claudia and he would say, ‘no, granddad’, meaning I don’t want to see this lady on the screen I want my granddad.

“That was really heartbreaking. It’s things like that that really, really upset me.”

The half-hour documentary by production company Glasshead, called Missing – The Claudia Lawrence Story, will be shown on Channel Four at 7.30pm on August 13.

It features interviews with Ali, as well as Claudia’s father, Peter Lawrence, her best friends Jen King and Suzy Cooper and reporters at The Press. The last time anybody heard from 36-year-old Claudia was at 8.23pm on March 18, 2009, when she sent a text to a friend making a loose arrangement to meet up later in the week. Shortly before, she spoke to her mother on the phone.

The following morning, Claudia never turned up for her 6am shift at the University of York’s Roger Kirk Centre canteen – a two-mile walk from her terraced cottage in Heworth Road.

North Yorkshire Police are now scaling down the suspected murder investigation, with only 16 officers left on the case, compared to 100 at the height of the inquiry.

But Ali’s plea remains the same – if anybody has any information that might help police to find her sister, please get in touch.

Phone North Yorkshire Police on 0845 60 60 247 or Crimestoppers anonymously on 0800 555 111.