Ng then testified that it was Leung’s “very smug” expression that invited him to “bring it on” and lob the pungent snack.

Former leader CY Leung’s ‘smug’ face invited me to throw a tuna sandwich at him, says Hong Kong pro-democracy campaigner

But magistrate So Wai-tak found that Ng was only making up excuses to rationalise his behaviour after he intentionally launched the attack to express his dissatisfaction with the government. So concluded the activist was an unreliable witness.

Ng said during his mitigation that he did not mind a heavy punishment. “I am deeply honoured to be able to do something for the underprivileged,” he told the magistrate. “I hope you understand that no deterrent sentence will work on me.”

Ex-leader CY Leung to blame for policeman being hit by sandwich I threw, Hong Kong activist says after failing to halt assault trial

But the magistrate replied that it did not matter if the motive behind the assault was noble.

“The court respects the freedom of expression but it will not tolerate violence,” So said. “A deterrent sentence is needed to prevent a repeat that will put the lives of public officers at risk.”

Ng had no prior criminal record. He was sentenced to three weeks in jail, but released on bail pending an appeal, on condition that he remain in Hong Kong and file his appeal papers on time.

Outside court, Ng called the case a political prosecution and accused the government of “using the judicial system as a tool to suppress opposition opinions”.

“Imagine getting [jailed] three weeks over a soft sandwich; how big a suppression will we face when we fight against other social injustice and stage bigger public actions?” he said.

His party colleague “Long Hair” Leung Kwok-hung added: “I’m hoping to do an experiment and buy 1,000 sandwiches to see how much they will hurt when thrown at a person.”