The best friend of murdered teenager Peter Hagan has described the moment he and his mates were subjected to a vicious attack involving knives, hammers, bottles and CS gas at a party, a court heard.

The 17-year-old witness, who cannot be named for legal reasons, arrived at the party, on February 16, on the second floor flat before Mr Hagan, and told the jury the mood at the time was "calm".

He told the Old Bailey today he had been invited by Jamilya Ferguson, the younger sister of two of the defendants, who was celebrating her birthday.

The flat is in Albon House, Nevilel Gill Close, Wandsworth.

But not long after Mr Hagan and another group of boys arrived, the party mood soured, from "good to bad", according to the young witness's evidence.

Initially, the witness said, four older boys had been talking in the flat's kitchen, while the rest of the guests were in the living room.

The four older boys, the jury heard, "started talking rubbish" to the younger boys.

"Peter said one of the boys had gone to get a knife," the witness said.

"There was a lot movement, and I saw a male go to the kitchen.

"I heard the knives, the cutlery, and we were figuring what to do.

"Two of the boys were arguing with Jamilya and one man sprayed CS gas."

The witness did not name him directly but described him as dark skinned, stocky and a "big man".

He added: "We went to the balcony. Both groups. But he sprayed it again.

"One of the men had a knife, Peter was getting stabbed, in his legs and upper body.

"The knife was all over the place."

The court was told the man with the knife was described as short, lighter skinned, with a short beard.

The witness then told the jury that a "very fat" man had tried to hit him with a hammer.

"I was defending myself, another one had a bottle," he added.

"We were trying to fight to get off the balcony "Peter was getting kicked in the head.

"Another man, who was older than the others, was holding a big knife.

"We ran out of the flat, but they were coming after us. One ran down the stairs, but saw Peter on the stairs. The man ran back upstairs."

Paramedic Joseph Locke told the court Mr Hagan was given 50 minutes of "continuous resuscitation" once he was found in the stairwell, to no avail.

The court then heard from forensic pathologist, Dr Simon Morris-Poole, who said Mr Hagan was ultimately killed by a stab wound to the left thigh which sliced his femoral artery.

He said there were four major wounds in total, one to the thigh, the arm, the buttock and the back.

Dr Morris-Poole told the jury the thigh wound was 13cm deep and 4.7cm wide, however, the arm injury was 8cm deep but was not fatal.

Mr Hagan, 16, of Brixton, bled to death in the stairwell of Albon House in the early hours of February 17.

Romell Martin, 22, of Fairgreen Road, Thornton Heath, Dean Harmes, 26, of Garratt Lane, Wandsworth, Maliki Ferguson, 21, of Albon House, Neville Gill Close, Wandsworth and Jermal Ferguson 23-year-old, who , are accused of his murder.

The trial continues