A 16-year-old accused of murdering a student told the Old Bailey he thought the man was a paedophile.

Defendant A took to the stand last week accused of the murder and robbery of "quiet and private" man Martin Thomas, 39, from Roehampton.

Defendant A, from Putney, is charged along with defendant B, 14, from Wandsworth, and Odel Munroe, 20, of Sudbury House, Wandsworth High Street.

The prosecution argues defendant A inflicted the fatal blow to Mr Thomas’s chest, but said all three were responsible for his murder.

Defendant A, who is 6ft 2in, took to the stand on Thursday. He was 15 at the time, on tag for previous offences and in year 11 at school, preparing to take his GCSEs.

He told the court he first met Mr Thomas and gave him his number at the end of 2013, at Putney station, after Mr Thomas asked him for cannabis.

He said Mr Thomas would call asking if he was in the area and added: "I just thought he was a bit too eager for weed. Why was he constantly phoning? On a few occasions he offered me £150.

"He didn't fully explain himself he just said 'go with the flow'. To be honest, my first reaction, I didn't understand. I thought this man was a paedophile."

He told the court he ignored Mr Thomas's calls but they did not stop.

On the day of Mr Thomas’s death, Tuesday, April 22, defendant A said Mr Thomas called asking for cannabis and he decided take him cannabis because he needed the money and Mr Thomas, he alleged, said he could have the £150.

He told the court he asked defendant B and Odel Munroe to come with him as "extra precautions" and would shout if he needed help. He also armed himself with his mother's kitchen knife to scare Mr Thomas if he did not let him leave his house in Huntingfield Road, he told the court.

When questioned by his lawyer Icah Peart QC what he thought the £150 was for, defendant A answered: "Probably to have his way with me."

He told the other two defendants to wait outside and said when he entered the house Mr Thomas closed the door behind him, leaving him feeling "nervous and anxious". A discussion about money turned violent when Mr Thomas reached for an ornament on a table, when the defendant pulled out the knife and pointed it at Mr Thomas, he claimed.

He said: "He lunged on me, I think I stumbled back a bit, a little stumble, I didn’t fall over.

He added: "He was trying to wrestle me to the ground.

"He had his arms around my waist and he was moving me from side to side. During trying to get him to the ground I got the knife which is in my hand and I started poking him in the back."

He managed to get the door ajar and call to his friends, who pushed their way into the house.

Defendant A said: "I don’t know whether it was the force from the door opening but he slumped to the floor.

"I think he gave up keeping me in the house because he saw the other two."

When asked how he was feeling at that point he said: "I was scared. I didn’t want to be there no more."

He said defendant B went upstairs and he followed to tell him they needed to go.

He told the court he felt terrified and ashamed adding: "I realised I lost my hat. I was bleeding and knew I was going to be arrested for some sort of assault."

At the time of the incident defendant A had a court-imposed curfew of 9pm.

His lawyer told the court of went three previous convictions, to which he had pleaded guilty to in youth court in May 2013, when he was 14 years old.

First was for criminal damage and common assault and a third was assault occasioning actual bodily harm.

The trial continues.