Police say that two officers were injured when trying to apprehend a man with a large knife outside Buckingham Palace Friday.
Kiana Williamson, an eyewitness to the attack, recounted what she saw to the BBC.
"We turned up and there was one police van and one car," she said, "there was also a civilian's car that had veered towards the police car."
"They were trying to get the man out of the car, shouting," she continued, "more police were arriving on to the scene and the man was fighting back."
"I saw one injured policeman with an injury to his arm, although it didn't look severe," Williamson explained. "He was being tended to by another officer."
"The man had been restrained and looked almost unconscious by the side of the road."
Another eyewitness told the Associated Press that her partner believed the man was carrying a sword, but that report has not been substantiated.
"The police didn't just run up to the car," she said. "There was some shouting prior to this; I couldn't tell you what, I was a bit panicked..."
"My partner saw a sword, which I didn't see, as well as a policeman with blood on him, looking like his hand or chest was injured," she added. "The police officer had it in his hand, walking away with it."
A detective superintendent gave an official account of the events to the press.
“A man in his mid-twenties has been arrested by police after they spotted a weapon inside his car," he said. "The quick and brave actions of both officers meant that the suspect was detained very quickly. No members of the public had any interaction with this individual at the scene. He will now be questioned by detectives in police custody. It is too early in this investigation to speculate any further.”
None of the royal family were in residence at the time of the attack.