Hong Kong police on Tuesday arrested a veteran pro-democracy politician who was granted bail last August for medical treatment after spending more than a year in detention on a subversion charge.

Albert Ho, 71, once led the city’s largest opposition group, the Democratic Party, and is a lawyer who runs his own law firm.

Police handcuffed Ho and took him away from his home in a vehicle, a Reuters witness said.

Neither police nor Ho’s law firm immediately responded to requests for comment.

Ho has been charged with inciting subversion under a national security law that China imposed on the former British colony in 2020. He pleaded not guilty.

He was granted bail last August, with media reporting at the time he needed medical treatment for lung cancer.

The judge who granted him bail told him if he committed any acts endangering national security “his bail will be revoked and he won’t be able to receive any kind of private medical care”.

This month, police arrested a veteran union leader, Elizabeth Tang, after she visited her pro-democracy activist husband in a high security prison. She was charged with collusion with foreign forces and granted bail.

Ho’s brother, Frederick Ho, was also arrested in connection with that case.

Albert Ho stands accused with two others, Lee Cheuk-yan, 66, and Chow Hang-tung, 38, of inciting subversion of state power under a China-imposed national security law, given their leadership roles in a now disbanded group called the “Hong Kong Alliance in Support of Patriotic Democratic Movements of China”.

The Asian financial hub returned to Chinese rule in 1997 under a “one country, two systems” formula granting it a high degree of autonomy but some Western countries say China is undermining those freedoms with the 2020 national security law.

Chinese and Hong Kong officials deny that and say foreign interference is endangering the financial hub’s stability and prosperity.