A man raped a lone dog walker because she looked like his ex-girlfriend, whom he went on to kill hours later, a court has heard.

Marvin Samuels attacked the 43-year-old woman as she walked her chihuahua around Welsh Harp reservoir in Brent, London, it is claimed.

The heavily-built, tattooed 31-year-old dragged her into the undergrowth, before ordering her to strip naked and raping her, a jury heard.

He then allegedly tried to strangle her with her scarf, before repeatedly beating her over the head with a bottle and tree branch and leaving her for dead.

Just hours later, Samuels stabbed to death his ex-girlfriend and mother of his child Sharlana Diedrick, 32, as she sat in her car near his home in Stonebridge, the Old Bailey heard.

He allegedly knifed the mother-of-four 16 times in the chest and abdomen at about 11.10pm on September 29 last year, before calmly walking away.

Neighbours reported hearing the mother-of-four screaming: ‘Help, somebody help, he’s stabbing me’.

Maureen Jones, who rushed to help, said: ‘As I got to the car, I saw her eyes were open and blood was around her neck – I could see cuts on her arm.

‘She took a gasp of air, and to me, it was like her last breath.’

Within minutes of the frenzied attack, shaven-headed Samuels sent his mother a text message with just a kiss in it and was later spotted on CCTV sprinting down Argenta Way in Neasden.

He was then seen creeping into the back entrance of a nearby Travelodge at 12.10am – only emerging again at 2.29am.

Wearing fresh clothes and a bandage around his hand, he handed himself into police at 3,30am, and confessed he had dumped his blood-stained clothes and changed at a friend’s house.

The woman he allegedly raped was found naked and badly beaten by her husband and his friends the next day.

She was taken to hospital, but has not been able to give an account of what happened to her.

Duncan Atkinson, prosecuting, said: ‘She and the defendant were complete strangers to each other. She simply was in the wrong place at the wrong time. She had a resemblance to a second woman who was attacked.’

He said that Samuels had claimed he had been ‘stressed’ about his relationship with Miss Diedrick at the time of the assault.

‘He attacked the woman while stressed about his relationship with Sharlana Diedrick. He said he knew what he was doing,’ said Mr Atkinson.

‘He encountered the women when when he was about to leave the reservoir, started to talk to her, pulled her into the undergrowth and hit her.

‘He then directed her to undress and then raped her. He then started to choke her with her scarf and struck her head first with a bottle and then a branch.

‘Having left her for dead, only a few hours later the defendant stabbed Sharlana Diedrick as she sat in her car using a knife which he had armed himself with in advance.’

He told the jury Samuels and Miss Diedrick had been in an on-off relationship which was marred by violence.

Before her death, the court heard Miss Diedrick had picked up Samuels in Watford and they had started arguing over their son’s childcare arrangements.

She had agreed to drive him to his mother’s home in Conduit Way, parking around the corner to avoid being seen together.

It is then that they argued again and he launched the frenzied stabbing attack, the jury heard.

Samuels surrendered to police in the early hours of the following morning and told detectives he was responsible for the assault on Miss Diedrick.

He claimed to have not been in the right frame of mind, but is yet to formally enter a defense of diminished responsibility.

Describing the stabbing, he told police: ‘I was feeling unusual. I was different that day, I wasn’t in my right mind. I was awful crazy.’

Mr Atkinson said: ‘The defendant admitted he had lost it completely. He further admitted stabbing Miss Diedrick in the car during the argument.

‘He described feeling not quite right in his mind. Miss Diedrick had not been violent to him and it was all him.

‘He would have stabbed her more had he not hurt his hand during the attack.’

Samuels told officers that his ex-girlfriend had begged him to stop, but he only relented when he realized he had suffered deep wounds to two of his fingers in the attack.

He also admitted raping the lone dog walker, and causing her grievous bodily harm, after forensics linked him to the assault.

However, he has denied her attempted murder and the murder of Miss Diedrick.

Mr Atkinson told the jury that they had to decide what Samuels’ mental state was at the time of both attacks.

The trial continues.