A 17-year-old fatally stabbed a former Lewisham teen with a zombie knife at a railway station after getting threats on Snapchat, a court has heard.

The 17-year-old is on trial at the Old Bailey accused of murdering Louis Johnson at East Croydon station in south London on the afternoon of January 27.

The defendant, who cannot be named because of his age, has admitted having a knife but denies murder.

The court heard that the youth had come to the attention of police for carrying knives in the past.

Giving evidence, the teenager, originally from Tooting, admitted that he regularly carried knives, having started at the age of 13 to "look cool".

He told jurors: "Lots of people my age carry knives. I had been targeted by people from Clapham Junction."

The defendant said he had seen a message on Snapchat threatening to stab him.

He said he first met Louis, who live in Tooting and Lewisham before moving to South Norwood, two-and-a-half years ago, saying he "tried to fight me".

The second time they met, Louis tried to "group assault" him, the defendant alleged.

On the next occasion, last August, the defendant said Louis jumped off a moped and pulled out a knife.

The defendant said Louis had also made threats against him on Snapchat.

On the day of the stabbing, the defendant said he set off to visit his mother in Tooting.

He was carrying a blade even though he had no reason to think he might bump into Louis at East Croydon station, he said.

He added: "I used to carry it in my waistband because I was going to an area where I knew I have problems."

The defendant told jurors he had walked up on to the overbridge at the station after finding himself on the wrong platform.

He said he stood at the top of platforms three and four, looking at the screen, before walking towards platform two.

When he looked down, he noticed Louis and another boy in front of him, he said.

"I heard a shout 'You' aggressively towards me.

"I thought he was going to stab me. I put my phone in my pocket. I saw him reaching for his waistband."

Tyrone Smith QC, defending, asked: "What did you think he was reaching for his waistband for?"

The defendant replied: "A knife."

The youth went on: "I pulled out my knife and thrust it towards him."

After stabbing Louis, the defendant said he made off because he "panicked" and wanted to "get out of the area".

Mr Smith said: "Why did you stab him?"

The defendant replied: "Because I thought he was going to stab me."

The lawyer asked: "Did you want to kill him?"

The youth said: "No."

The trial continues.