The Duchess of Cambridge's uncle has admitted hitting his wife in the face and knocking her to the ground after a drunken argument on the way home from a charity event.
Gary Goldsmith, 52, used a closed fist to attack Julie-Ann Goldsmith outside their home in Wimpole Street, central London, at around 1.20am on October 13 this year.
He appeared at Westminster Magistrates' Court on today, and pleaded guilty to one count of assault by beating.
Prosecutor Kate Shilton told the court Mrs Goldsmith fell down after her husband threw what was described by their taxi driver, Daniel Shepherd, as a "left hook".
She said: "The argument took place in the back of a taxi.
"They both got out of the taxi and he (Mr Shepherd) describes Mrs Goldsmith slapping her husband to the face.
"He then describes how Mr Goldsmith punches her hard in the face using a left hook.
"Mrs Goldsmith has then fallen backwards. He says 'She appears to be unconscious, she isn't moving'."
Mrs Goldsmith was knocked to the ground, where she remained with her eyes closed for around 15 seconds before waking up and staggering to her feet, the court heard.
Ms Shilton said: "She (Mrs Goldsmith) then becomes upset, starts crying and uses some railings to assist her."
After the incident, Goldsmith was described as "panicked and walking in and out of the house, trying to get her to go back in the house".
The court was told that, when the taxi driver challenged Goldsmith over his actions, he then became aggressive towards him.
Mrs Goldsmith asked Mr Shepherd to call the police.
At the police station, Goldsmith told officers he had pushed his wife hard with his left hand, but denied using a hook.
The court heard that he was apologetic for his actions.
Goldsmith will be sentenced at the same court on November 21.
Chief Magistrate Emma Arbuthnot said: "I am excluding custody and looking at a community order.
"But I am really looking at how to protect this lady from this man."
Goldsmith is the younger brother of Carole Middleton, and attended the weddings of both Kate and Pippa.
He was brought up with his sister in Southall, west London. Their mother worked in a shop and also did accounts, while their father was a painter and decorator.