One of Russell Brand’s accusers felt safe inviting him to her room because she assumed he was gay — until he raped her after doing “silly walks like Basil Fawlty” in “budgie-smuggler” undies, prosecutors told the star’s rape trial Wednesday.

Brand, now a married dad of three living in Florida, met the unidentified 20-something woman at a conference for the UK’s left-wing Labour Party in Bournemouth in 1999 and won her over by being “very polite, courteous and complimentary,” jurors in the UK trial were told.

He said “she was pretty, always in a gentlemanly way, and she was flattered,” prosecutor Riel Karmy-Jones said, describing the encounter, the BBC reported.

“But at that point, she assumed he was gay – he gave no indication of being attracted to her.” 

She invited him to her room, where she became alarmed when the flamboyant comedian stripped down to wearing just “budgie smugglers,” the UK nickname for tight-white underpants, prosecutors said.

Brand then started “prancing around the room” and doing “silly walks like Basil Fawlty,” the prosecutors said of the 70s sitcom character played by “Monty Python!” star John Cleese.

“She asked him why he had taken his clothes off and he said something along the lines of, ‘It’s okay, it’s just how I am… don’t worry, I’m mostly naked at home,” Karmy-Jones said.

The woman “froze” before Brand allegedly sexually assaulted her, during which she “drifted out of her head,” Sky News reported.

Brand then “behaved as if nothing had happened,” as the accuser felt “ashamed” and “chastised herself for inviting [Brand] back to her room.”

“Throughout, she felt it was her fault,” Karmy-Jones said, adding alleged predator Brand “found a victim.”

But Brand “behaved oddly” the day after the alleged attack, with Karmy-Jones claiming he told pals they had “leave [Bournemouth] immediately.”

The alleged rape is the earliest offense that has been leveled against Brand, whom prosecutors called a “ruthless sexual predator” who bragged about plans to bed “5,000 women.”

Brand has been accused by six women and is charged with three counts of rape, three counts of sexual assault, and one count of indecent assault tied to alleged incidents that occurred between 1999 and 2009.

He has always vehemently denied the allegations and has pleaded not guilty to all charges.

Brand rose to prominence in the early 2000s, hosting his own BBC radio show. He appeared in films including “Forgetting Sarah Marshall” and “Rock of Ages.”

With Post wires.