A youth pulled out a knife like a character from Netflix drama Top Boy and stabbed 15-year-old Elianne Andam on the ground as she begged him to “stop”, a court has heard.

Hassan Sentamu, 18, had lashed out at the schoolgirl after refusing to hand back her friend’s teddy bear after they split up, the Old Bailey has heard.

When Elianne grabbed a bag of his clothes as “a joke”, Sentamu “got mad”, chased and repeatedly stabbed her, jurors were told on Tuesday.

As she collapsed outside the Whitgift Centre in central Croydon, south London, Sentamu fled – dumping the knife in nearby Cedar Road.

He was arrested within 90 minutes after a police officer stopped a number 64 bus near his home in New Addington.

Sentamu’s ex-girlfriend described events leading up to the attack on her friend before school on the morning of last September 27.

In a video interview played in court, she told police she realised something was wrong when he turned up for a planned exchange of their belongings wearing gloves and a mask.

She knew Sentamu had an “anger issue” – and likened his demeanour to a character from the London-based crime drama Top Boy, the court heard.

She said: “I thought he was gonna hit me. I thought that he had something on him because … watching shows and stuff like, for example, Top Boy, whenever someone’s about to get killed they always have on specifically black gloves.

“I’ve never seen him wear black gloves, it’s not cold outside.”

She said: “I was saying ‘can I have my stuff back?’ like outside the Whitgift Centre where the bus stop is.

“He looked at me … and rolled his eyes a bit … and said ‘I don’t want to hurt you’ … not like in an emotional way … like he’s warning me.”

She went on: “I was saying ‘Where’s my teddy? Where’s my teddy? Where’s my teddy?’.

“He was looking me up and down, just saying ‘look at you, look at you’ … it was sort of like a disgusted way.”

Asked how it made her feel, she replied: “Not too good.”

The girl, who cannot be identified for legal reasons, went on: “Elianne ran behind him, grabbed the bag and started running and laughing as a joke. It was the type of thing that Elianne would have done.

“At first I was laughing a bit ‘cos it was a joke and then I got scared ‘cos then Hassan got mad.”

She told police: “He then lifted up his hoodie quick, pulled out something and I saw a big knife.

“I turned around for one second then I saw her on the floor like trying to say ‘stop’, basically with her hand out. He was there like over her, bending.

“I just saw Elianne on the floor like backing up on the floor with her hand out like this basically saying ‘stop, stop, stop’ and I’m pretty sure I saw him bend and like try and do something else, like stab her again.”

When she turned around again, Sentamu was gone and she ran as passengers at a nearby bus stop began “shouting and screaming”, she said.

Before arranging the meeting, the girl said Sentamu had got angry and sworn at her during an argument over the phone.

She said: “I just told him never, ever speak to me like that ever again ‘cos I said ‘I’ve never been spoken to like that in my life’.

“I said no man should speak to a girl like that and he said ‘oh well, there’s a first time for everything’.

“And I said so that’s how you want to be like, portrayed as someone that wants to be talking to females like that, basically.”

Pc Alex Smith described the “scene of chaos” when he arrived outside the Whitgift shopping centre on Wellesley Road.

He told jurors: “There were people screaming, shouting, people running away. I knew a serious incident had occurred.”

He grabbed a first aid kit and took over chest compressions on Elianne, who was not breathing.

Pc Ben Carter arrived soon after and used a bandage to apply pressure to Elianne’s neck wound.

He told jurors: “Next to Elianne there was a school bag. Inside was a school planner that had her name on it and that was how we were able to identify her.”

Despite the efforts of members of the public and the officers, Elianne was pronounced dead at the scene at 9.21am.

Pc Peter Nolan said he was at the police station when he heard a young woman had been stabbed and a colleague relayed details of the suspect.

Sentamu, then aged 17, was described as wearing a “distinctive” multi-coloured “Trapstar” hooded top and was believed at the time to be the boyfriend or ex-boyfriend of the victim, Pc Nolan said.

Giving evidence, Pc Nolan told jurors: “Whilst driving along King Henry’s Drive I saw a 64 bus from Croydon, so I decided to stop the bus and see if anyone matched the description on the bus.”

Pc Nolan’s body-worn video captured the exchange as he detained Sentamu.

Asked his name, the defendant said he was called “John” before he handed over his Oyster card with his real identity on it.

The defendant asked why, when the officer told him to put his hands behind his back.

The officer then called for “urgent assistance”, informing the defendant: “You are under arrest on suspicion of GBH, stabbing your girlfriend. Where’s the knife? Where’s the knife?”

Pc Nolan told jurors: “All I knew is that a young girl had been stabbed and the officers were doing what they could to keep her alive.

“One of the officers that turned up said to me the female had sadly passed away and it was now murder.”

Prosecutor Alex Chalk KC asked the witness if he noticed anything about the teenager he had detained.

The officer replied: “I believed what I saw was a smear of blood on his thumb.”

He told jurors he called for evidence bags to put over the handcuffed suspect’s hands before he was put in a van and taken into custody.

Jurors watched CCTV footage of the incident in which Elianne was fatally stabbed and images of the defendant running away.

Moments before, Elianne appeared to be caught up in the drama when she recorded a short video clip on Snapchat.

Sentamu, who was studying sports science at Croydon College, has admitted manslaughter but denied Elianne’s murder on the basis of “loss of control” because he has autism.

He denies a charge of having a blade, claiming he had a “lawful reason” for carrying it.

The Old Bailey trial before Mrs Justice Cheema-Grubb continues.