Pc Andrew Moore said he was surprised to find Ali Dizaei with no clothing out of place after an apparent street scuffle with another man.
Southwark Crown Court heard the officer was one of several who responded to a call for urgent assistance from Dizaei at the Persian Yas restaurant on July 18 2008.
Giving evidence today, Mr Moore said: "He was incredibly smart, as most senior officers are dressed.
"Bearing in mind I had just gone to urgent assistance, an off-duty assistance, that is not always the scene I would have expected to turn up to."
He added: "Ali Dizaei was holding the male. He was incredibly smart. His clothing was not dishevelled at all and the scene appeared very calm."
The senior officer later told his colleague: "I cannot believe this has happened. I even know the guy," the court heard.
Dizaei, 47, one of Britain's most senior Asian officers, is on trial accused of misconduct in a public office and perverting the course of justice.
Prosecutors claim he falsely arrested Iraqi web designer Waab al-Baghdadi, lied about an assault and left the young businessman facing a police inquiry.
The jury has heard the two men argued over money Dizaei may have owed for a personal website after the pair met by chance at the High Street Kensington eatery.
Dizaei drove to the restaurant, which was owned by a friend, after attending a Scotland Yard ceremony for new officers.
A second officer who was also among the first at the scene, Pc Andrew Collett, also gave evidence today.
He said he was surprised when officers pulled Dizaei's business card out of the back trouser pocket of a handcuffed Mr al-Baghdadi.
Mr Collett said: "The reason I recollect the card is I felt it was a little bit odd that he had Mr Dizaei's business card."
The jury watched CCTV footage of a police car pulling up outside the restaurant and an officer walking inside asking for help.
Mr Collett said he was met with silence from customers, who included Mr Dizaei's wife, when he asked if an officer needed help.
He said: "I went in there and asked if there was any police officer who required attention at that particular time.
"I was met with silence despite the premises being quite busy with customers.
"Usually if there is urgent assistance there is a whole lot of violence, usually people will come up to you.
"I asked two or three times, I was very surprised."
The jury heard the officer found Dizaei, dressed in a white police shirt and epaulettes, with Mr al-Baghdadi a short distance away in a sidestreet.
Describing Mr al-Baghdadi, Mr Collett said: "He was calm, but he was complaining, generally moaning about how he had been treated when he was arrested. That is not an unusual situation."
The court heard Dizaei was holding his left arm and shaking his wrist as if injured. He handed an officer the mouthpiece of a shisha pipe and said he was attacked with it.
Later, Pc Darren Christopher told the court that Mr al-Baghdadi started to talk to him as he was transferred in custody to the police station.
Mr Christopher said Mr al-Baghdadi told him he had designed Dizaei's website and the police commander owed him money.
"I saw him tonight in here and thought I would try to get the money he owed me," Mr al-Baghdadi said, the court heard.
"He's taking liberties. He's only arrested me because he's a commander, a high-ranking police officer."
Duty inspector Jaiye Warwick-Saunders, who also attended the scene, said Dizaei was "staring straight ahead" and appeared distracted when he first arrived.
He added that Dizaei did not seem keen to be taken back to the station.
Mr Warwick-Saunders said: "He appeared to be - disinterested is too strong a word - his mind was on something else."
Asked about Dizaei's injuries, Mr Warwick-Saunders said there did not appear to be any serious injury.
He said the commander told him that he was in his car with his wife when Mr al-Baghdadi began banging on the window, "shouting and swearing and gesticulating".
Dizaei told police that after making sure his wife was safely inside the restaurant, he drove after Mr al-Baghdadi and got out to speak to him.
Dizaei told the duty inspector the man "produced a small ornamental instrument and threatened him", adding it was "a pointed object".
The trial was adjourned until tomorrow, when Dr Maureen Heath, a forensic medical examiner with the Metropolitan Police who examined Dizaei on the night of the incident, will give evidence.
