A teenager accused of stabbing a 17-year-old boy to death at an outdoor party told a friend to “get the shank” earlier in the night, a court has heard.

The female party guest says she heard another teenager "talking about a knife" shortly before he allegedly stabbed Charlie Cosser in the chest.

Charlie was fatally wounded at the event attended by dozens of people at a farmhouse in Warnham near Horsham.

The defendant, who cannot be named because he is underage, denies murder and having a bladed article.

Prosecutors allege the fatal injuries took place when a fight broke out between the defendant, Charlie, and two other boys on the dance floor after the defendant and his friends were asked to leave the "BalFest" party.

A female party guest told Lewes Crown Court sitting in Brighton she saw the defendant, who was 16 at the time, “talking about a knife” with a friend after a third male’s arrival made them agitated.

She told the court that when the boy arrived in a car, the defendant and his friend “both seemed very shaken up almost.

“They both seemed angry and nervous.

“[The defendant] turned to [his friend] and told [him] to get the shank.”

The friend “put his hand in his bag as if he was holding what I thought could be a knife”, she added.

The young woman, who cannot be named also due to her age, told the court she then witnessed the pair walking towards the man whose arrival had made them “angry and nervous”, and went to warn someone she thought they might stab him.

She later saw the trio together at the party, and there seemed to be “no problem”, jurors heard.

Video footage previously played to jurors showed revellers just before midnight dancing to Toxic by Britney Spears under disco lights in a marquee.

A fight is then visible in the background with punches being thrown and the recording shortly ends.

Charlie died in hospital two days after he was stabbed three times at Balmohano Farmhouse.

He was still conscious when police arrived at 12.30am and was able to tell them his name, address and date of birth, prosecutors have said.

He suffered a cardiac arrest on the way to hospital, with internal bleeding caused by a cut to his aorta, the main artery from the heart.

The teenager, from Milford, Surrey, died on July 25.

The trial continues.