A young police officer has told a court of her shock at discovering the gruesome remains of Pc Gordon Semple.

Pc Charlotte Edwards, who joined the force two years ago, was first to attend Stefano Brizzi's flat with her colleague Pc Helen Savage, the court heard.

The pair had been called to investigate a pungent smell coming from the property on the Peabody Estate near Tate Modern six days after Pc Semple disappeared on April 1.

READ MORE: Man 'called by as sadomasochist was strangling PC Gordon Semple'

The 50-year-old defendant answered the door wearing pink Y-fronts and steered them towards the bathroom, the court heard.

Pc Edwards told jurors it smelled strongly of chemicals and "gone off meat".

The bath was full of "flesh globules" floating in murky turquoise water, she said.

Brizzi allegedly told Pc Edwards: "I've tried to dissolve the body. I've killed a police officer. Satan told me to."

READ MORE: Man 'called by as sadomasochist was strangling PC Gordon Semple'

Pc Edwards said she looked in a black bin bag on the floor and saw what reminded her of a chicken carcass.

The floor was slippery as if covered in a "layer of slime", she said.

The officer, who at the time was unaware an officer was missing, encouraged Brizzi to get dressed so they could get him out as "calmly as possible", the court heard.

Brizzi was led away by Pc Savage and two paramedics leaving Pc Edwards alone in the flat awaiting more officers to arrive.

The court heard it was only then that the enormity of what she had witnessed hit home, she said: "I was feeling quite shaky. I realised what was going on, I didn't realise it was a police officer."

Later, Brizzi told her that he had flushed "flabbery bits" - taken to mean internal organs - down the toilet five minutes before, the court heard.

The officer went on: "He said 'is suicide legal because if I have to do a life sentence then I want to kill myself'.

"I tried to reassure him, not to talk about the long-term future. I was almost trying to console him."

He told her he was from Italy and had worked as a developer at financial giant Morgan Stanley and had taken crystal meth, the court heard.

READ MORE: Man 'called by as sadomasochist was strangling PC Gordon Semple'

Pc Edwards said that he then told her a voice told him to "kill kill kill".

He allegedly said: "I promised the devil I would kill at first chance."

Pc Edwards told the court that leaning forward almost whispering, he went on: "I didn't know who he was. I didn't like him. He just sat on my bed masturbating.

"I didn't know he was a police officer until after I killed him."

The court heard Brizzi told her he had written about Satan as a fetish online, saying: "I'm from a Catholic family so when I found out I was gay I found out I was from Satan.

"I met a guy online who wanted to pretend he was 15 and me a paedophile."

Pc Edwards said she thought he was talking about the 59-year-old victim.

Brizzi denies murder and the Old Bailey trial continues.