For 53 years, the family of Mary Bastholm have lived with the anguish of not knowing where her remains are after suspecting she was killed by Fred and Rose West.

But there was last night signs of a breakthrough as police began a dig at a cafe where a TV crew filming a ­documentary on the waitress claim they found evidence of a body. Detectives said the development was “significant”.

Mary was 15 when she vanished from a Gloucester bus stop in 1968 while on her way to visit her boyfriend.

It has long been rumoured Fred knew the youngster as he often visited the Pop In cafe where she worked.

The couple are among Britain's worst ever serial killers

Rose’s former solicitor, Leo Goatley, claims tragic Mary could have been the couple’s first murder together.

He said: “I think there is evidence the Mary Bastholm murder was [Rose’s] ­initiation into the whole thing.

“It is not like the Pop In cafe was not on the police radar right from the start.

“In fact I believe they have been in there before but without clear evidence could not pull a going business apart.

“I think Mary was a sore point because there was so much compelling evidence that Fred and even Rose West were involved in her disappearance. I just hope the police do find ­something that finally gives closure for the surviving members of Mary’s family.”

Fears have been raised for the fate of Mary

Gloucestershire Police Assistant Chief Constable Craig Holden said: “This could be a significant ­development.

“On the basis of the information provided to us, we consider this to be new and ­potentially important evidence in the case of Mary Bastholm.”

Fred is believed to have confessed his involvement in Mary’s disappearance to his son Stephen while in prison awaiting trial – but he killed himself in 1995 aged 53 before he could face justice.

It has also been rumoured the serial killer, a builder and odd job man, filled in the basement at the Pop In cafe.

This is the first time a detailed search of the property, now the Clean Plate Cafe, has taken place after a former police chief insisted in 2012 there was “no evidence” Mary was buried there.

Police guard the rear of the Clean Plate cafe in Glouceste

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A white tent was erected outside the building and officers were seen carrying out evidence bags. The dig is expected to last a number of weeks.

Mary’s family have repeatedly asked Rose to break her silence on the case but she has so far refused.

Sources confirmed her brother Peter died last year aged 75. In one of his final appeals, he said: “I think Rose knows exactly what happened to Mary.

“Whether she will ever disclose it I really don’t know.”

Fred and Rose, 67, buried most of their victims in the basement of their home in Cromwell Street or at Fingerpost and Letterbox fields. There was no trace of Mary at any of those sites.

He was charged with 12 murders and in 1995 his wife was convicted of 10.

She is serving a life sentence.