The former Greens leader, Bob Brown, was molested by a choirmaster while at school in the 1950s, a Sydney court has heard.

Brown was giving evidence in a case against Ian Douglas Davidson, a former teacher at Sydney Grammar’s St Ives preparatory, where he is accused of 14 counts of indecent assault dating back to 1962.

None of the charges, which the 84-year-old denies, relate to Brown.

Brown told the court via video link that he was “fondled” by Davidson in an empty classroom after choir practice and again in a storage shed, interrupted only by “a knock on the door” from the school principal, the Daily Telegraph reports.

Another alleged instance took place on a steam train between Armidale and Tamworth.

“He sat down next to me and fondled me in the box carriage,” Brown said. “It was dark and I don’t think the other boys could see what was going on.

“I was highly embarrassed by the event.”

The incidents took place in 1956 when Brown was in year six.

Under cross-examination from Davidson’s defence, Brown said he had a “very clear recollection” of the events.

“I was so embarrassed, it has burned into my mind.”

Brownwas a founding leader of the Australian Greens and retired from the Senate in 2012 after representing Tasmania for 16 years.

The trial continues.