It is alleged the 42-year-old groped and sexually assaulted her before attacking her with a knife in her flat in the city’s Promenade Court.

During the first day of evidence, jurors heard the 999 call made by Ms Robertson’s partner, Charles Skinner, after he discovered her lifeless body.

Mr Skinner told an emergency call handler that he found his girlfriend, known as Meg, covered in blood in her home and said: “I know she’s gone.

“How am I going to explain this to her son and daughter? I walked in and found their mother lying dead.”

He said that the main entrance to the block was open so he went to her flat, but when he knocked on her door he failed to get an answer so shouted out to the 54-year-old, but still got no response.

He said: “Something told me something wasn’t right.”

The witness said he then tried the door to the flat and unusually found it was open. Through frosted glass on a bedroom door he could see someone was lying on the floor.

Mr Skinner said he had to barge open the door to get access and that sheer panic set in.

He said: “I just went to see if I could find a pulse. To me she felt cold.”

He contacted the emergency services.

Duncan is also accused of attempting to defeat the ends of justice by changing out of and washing bloodstained clothes and trainers, washing or discarding a bloodstained knife, hiding from police and providing false personal details to officers.

Duncan has lodged a special defence of incrimination in relation to the murder charge.

The trial before judge Lady Scott continues.