Prince Harry's friend Thomas van Straubenzee feared he was going to be stabbed when he was mugged by two men last November, a court has heard.
Thomas van Straubenzee, 29, was robbed while walking home from work, Kingston Crown Court was told.
Daniel Robinson, prosecuting, told the jury that van Straubenzee was mugged on the west side of Battersea Park.
"He was on one of his mobile phones to a friend of his, and a man approached him and grabbed him by the throat.
"A second man almost immediately ran at him and knocked him over, in something like a rugby tackle.
"One of the robbers sat on the lower half of his body, the other robber put his knee on his neck, and his mouth was covered by one of their hands.
"One of them started to go through his pockets, and the robbers told him that they had a knife.
"They took his phone off him, and Mr van Straubenzee handed over the rest of his property, because he thought he was going to be stabbed.
"They took his two mobile phones - one a Nokia, one a BlackBerry - and his wallet with its contents.
Winful Taylor, 27, of Stockwell, south London, denies robbing Mr van Straubenzee of two mobile phones and his wallet and its contents on 30 November last year.
Thomas van Straubenzee has long been a close friend of Prince Harry and Prince William. He attended a charity roller disco organised by Kate Middleton in 2008.
Taylor was arrested two days after the robbery at a hostel where he was living in Streatham, south London.
He had two mobile phones with him in a bag. One was a Samsung and one was Mr van Straubenzee's red Nokia, Mr Robinson said.
Taylor denied responsibility for the robbery, and said he bought the Nokia for £20 the previous day from a friend.
"He said he had not used the phone to make any calls, but that was a lie," Mr Robinson said.
Police found that the sim card from the Samsung phone had been used in the Nokia as soon as 80 minutes after the robbery, he added.
"The prosecution say he was caught out in clear lies about the circumstances in which he came to be in possession of the phone," the prosecutor added.
"He was one of the robbers, and that's why he lied about it."
Mr van Straubenzee made a statement Mr Robinson read to the jury which said he finished work in Chelsea that day and started to walk home.
"I was on the phone to a friend of mine and was not paying attention to anybody around me," he said.
One man approached him "from nowhere", grabbing him by the throat with one hand and the arm holding the phone with the other.
"A second man barged into me, which made me fall to the ground on my back."
He started to shout for help, but they told him they had a knife and to stop shouting.
"I was in fear of being stabbed," he said.
Items he handed over included £90 cash and a red leather diary.
Thomas van Straubenzee with Prince William in 2005