Russell Brand had an “insane sexual appetite” and his bad behaviour was “normalised and dismissed” by those around him, his former personal assistant has told a court.

Helen Berger alleged she had seen Brand treat women badly and that she once had to stop his mother and girlfriend walking in on him having sex with someone in his dressing room.

She also told the court she had overheard the comedian receiving oral sex in a toilet cubicle and once found a celebrity leaving his bedroom in the morning.

Brand, 51, faces three charges of rape, three of sexual assault and one of indecent assault against six women, in allegations spanning 10 years from 1999. He denies all the charges.

Wearing a grey suit and white shirt, Brand sat still in the dock as statements from prosecution witnesses were read to Southwark crown court on Monday.

Berger worked for Brand from June 2006 to February 2007, when he was at the height of his fame.…