The royal Prince was spotted arriving at Ms Brudenell-Bruce's exclusive London apartment, with security men in tow, at 9pm in his top of the range Audi.
He was seen leaving in the Audi the following morning, arriving back at his home in St James Palace at noon on Monday.
A witness said: “I saw Harry arrive at her house in his car. There was a team of protection officers with him travelling in a separate Range Rover.
"He got out and went inside. They waited outside. I didn't see him again until he emerged the following morning.”
Mr Brudenell-Bruce lives just yards from her ex-boyfriend the Formula One racing driver JENSON BUTTON.