On Tuesday, Cheng admitted going to Mong Kok on November 25, the day before the alleged assault by Chu, during which he claimed he was kicked and injured by an officer he identified as PC9401.

At the time he posted on Instagram: “Brain-dead 9401, I will remember you kicked me.”

But the court heard he did not report the matter to police, or ask a doctor to examine that injury even while he was checking for injuries from the baton strike he got a day later.

That medical examination on November 28 found that he suffered three injuries, including a horizontal, linear injury on the left of his neck.

Joshua Wong and other Occupy leaders allowed to appeal against jail terms

In court, Cheng testified before Principal Magistrate Bina Chainrai that he sustained injuries on his right shin, right elbow and the right part of his neck outside the bank on November 26.

Defence lawyer Peter Pannu pointed out that that account was different from what Cheng told police. Cheng first reported that Chu caused injuries to “the back side of my head” before making another statement that identified his injury “in the middle between the left side of the neck and the shoulder”.

When asked to explain the discrepancy, Cheng replied that the officer who took the report had got mixed up. “Because you can see from the police video it was really on the right,” he said.

But he was then shown another statement, which recorded that he “suddenly felt a hard object hit the back side of my neck on the left”.

“So a different officer made a mistake?” Pannu asked.

Cheng made a loud sigh, and leaned back and forth on the witness stand. He briefly covered his face with both hands before flipping through his statements in a quick motion.

“Sorry, excuse me, perhaps I did not remember that,” he said. “I was confused because this has lapsed for three years.”

Later he added: “Let’s not talk about left or right. The back of the head and the neck are more or less the same body part.”

Pannu then suggested that the downward movement of the baton had never touched any part of his neck or the back of his head.

“I put it to you that the defendant impacted you between your shoulder blades at the back,” Pannu said. Cheng disagreed.

But the lawyer went on: “Witness, you have exaggerated your injuries, your sufferances and the severity.”

“I disagree,” Cheng replied.

“I put it to you,” Pannu continued, “that your anger against PC9401 for the events on November 25 has meant that you have gone on to exaggerate and take revenge against the police.”

Cheng again disagreed.

The trial continues.