A man accused of murdering a police officer then trying to dissolve his body in acid answered his door wearing Speedos and Aviator sunglasses, a court has heard.

Neighbour Steve Harris said he thought the smell coming from Stefano Brizzi's flat was like a "dead body" from the start.

He was giving evidence in the trial of former Morgan Stanley worker Brizzi, 50, who is accused of murdering Inverness-born Gordon Semple and then trying to dispose of his body in an acid bath.

Describing a doorstep exchange on April 4, the witness said: "I said to him 'excuse me mate, there's a complaint about a bad smell in the block'.

"He said to me 'I'm sorry about that, I'm just cooking for a friend, that's the reason I've got the candle on the stairs'."

On April 7, he told his brother Martin, who called police and produced an official-looking Coastal Forces Veterans Association badge to confront the defendant.

When Brizzi opened the door, he was wearing Aviator sunglasses and looked like actor Tom Cruise in the film Top Gun, the witness said.

Martin Harris told jurors the smell was by now "putrid" and Brizzi was dressed only in Speedos-style attire.

He said: "This gentleman opened the door to me. He was trying to put his glasses on and trying to put a bathrobe on. He was cool as a cucumber.

"I knew something was wrong. If you've got a smell like that, you know what it is. I smelt it before many years ago."

Another witness said Brizzi turned up at a meeting of Crystal Meth Anonymous (CMA) sporting a Breaking Bad T-shirt.

Brizzi was allegedly a fan of the hit TV show in which the main character, chemistry teacher Walter White, produced crystal meth and, after poisoning a rival, dissolved the body in acid.

Alexander Roberts said the defendant had worn the T-shirt to a CMA meeting and posed in it in a Facebook photograph.

Mr Roberts also said the defendant was "dark" and had talked about Satan during discussions.

Mr Semple's partner, Gary Meeks, reported the victim missing the day after he had met his death in Brizzi's flat, the court heard.

He made a statement to police on April 5, before the dismembered body of his partner of 25 years was found.

In it, Mr Meeks described the officer as a "very sociable person" with lots of friends at work and in the security trade.

He said he last saw his partner on the evening of March 31, when Mr Semple went to bed and he stayed up for an hour watching television.

When Mr Semple got up for work as usual, Mr Meeks was asleep. At about 2pm, Mr Meeks called to say there was shepherd's pie in the fridge for dinner and they arranged to meet later at their local pub.

His last contact with Mr Semple was to ask him to record Gogglebox on the television at about 7.45pm, the court heard.

He said: "The phone was answered but it was a muffled sound, like a pocket dial. I thought I heard breathing, I thought I heard a door. I thought I heard someone speak.

"I was concerned about him and texted him saying 'Not home yet, I can hear noises'. I was very worried. On Saturday morning I texted to say I was reporting him missing to Charing Cross."