The estranged husband of a woman who vanished more than 45 years ago has told a court the man accused of her murder “didn’t say a word” when he was asked if he could help in the search for her and her three-year-old son.

William MacDowell, of Penrith, Cumbria, is accused of murdering his son Andrew MacRae and 36-year-old Renee MacRae in November 1976.

Gordon MacRae took to the witness stand at the High Court in Inverness on Wednesday.

The 85-year-old told the court that he and Mrs MacRae did not have a brilliant marriage, but when they split they had an “amicable” relationship.

The court was told he knew she was involved with somebody else, but despite repeatedly asking if it was someone he employed at Hugh Macrae Builders Limited, she would not reveal who it was, and he said he would sack them if he had found out.

Mrs MacRae, of Inverness, has not been seen since the night of November 12, 1976, and her disappearance sparked a huge police investigation.

MacDowell is charged with assaulting Mrs MacRae and their three-year-old son at the Dalmagarry layby on the A9 trunk road south of Inverness, or elsewhere, by means unknown, and as a result murdering them.

He is also charged with disposing of their bodies and belongings by means unknown.

Mr MacRae told the jury on Wednesday that he asked MacDowell, who was company secretary, into the boardroom in the days following the discovery of a burnt-out BMW in the case, and after he found out it was MacDowell who was involved with her.

Mr MacRae said he told him: “If you can help the police in any way, please do.

“He didn’t say a word the whole time in the boardroom. Not a word.”

He then fired MacDowell because of the relationship, the court was told, and he has never seen him again.

Murray Macara KC, cross-examining Mr MacRae, asked: “When police became involved, did you at any stage feel police suspected you might be involved in Renee’s disappearance?”

Mr MacRae said he did not, and then told the court he remembered that police had asked to search his house.

MacDowell, 80, denies all charges against him, and has said he was at home that evening after work.

He has lodged a special defence of incrimination and alibi, and claims it was Mr MacRae, acting with others, who committed the alleged crime.

Speaking in archive footage shown to the jury, Mr MacRae told BBC documentary makers: “I would hate to think it wouldn’t be solved, not only for everybody’s sake but I’d like justice to be carried out.

“I’m quite sure the police will get to the bottom of this one.”

MacDowell is also accused of setting fire to the BMW, disposing of a pushchair, and of a boot hatch from a Volvo, and it is alleged he did so to avoid detection, arrest and prosecution.

The trial, before Lord Armstrong, continues and is expected to last four weeks.