David Gilroy, 49, showed no emotion as he was led from the dock at the High Court in Edinburgh.
Lord Bracadale told Gilroy he had shown “quite chilling calmness” in carrying out an elaborate plan to conceal Ms Pilley’s body after murdering her, by unknown means, on 4 May, 2010, as she arrived at the office in Edinburgh city centre where they both worked and had become lovers.
The body is believed to be somewhere in Argyll.
The judge imposed the mandatory life sentence for murder, and set the “punishment part” – the period Gilroy must serve before becoming eligible for parole – at 18 years.
“It seems you are the only person who knows where her body is,” Lord Bracadale told Gilroy. “I hope a day will come in your life when you feel able to disclose that information. That might bring some comfort to her bereft family, particularly her mother and father who, after giving evidence, sat with quiet dignity throughout the rest of the trial.”
Robert and Sylvia Pilley attended the hearing, but declined to comment.
Gilroy’s father said there would be no comment from his family. Gilroy’s wife, Andrea, was not in court.
Last month, a jury convicted Gilroy, of Silverknowes Brae, Edinburgh, of murdering Ms Pilley, of Whitson Road, Edinburgh, in Thistle Street, and attempting to defeat the ends of justice by disposing of her body.
Both had worked for Infrastructure Managers, and they were involved in a relationship until shortly before the murder.
Gilroy had denied the offences, and yesterday defence counsel Jack Davidson, QC, said: “He maintains his position.”
Mr Davidson told Lord Bracadale that Gilroy, married with two teenage children, had no criminal record, and once had received a bravery award from the then First Minister, Jack McConnell, for helping catch a criminal. “His family continue to be supportive of him,” said Mr Davidson.
Passing sentence, Lord Bracadale said: “Suzanne Pilley was obviously a respected and well-liked member of staff in the office in which both you and she worked. In May 2010 she was starting a new chapter in her personal life and that included bringing to an end her relationship with you. On 4 May she set out to go to work pretty much as usual: the CCTV footage showed her getting off the bus in Princes Street and making her way to Thistle Street.
“Then she just disappeared, and the jury were satisfied on the evidence before them that that was because you murdered her and disposed of her body.”
The judge said life imprisonment was the only sentence for murder.
“Having regard to all the circumstances, I order that you serve a punishment part of 18 years.”