Rolf Harris's daughter broke down in court today as she described the "utter shock" of discovering her father had an affair with one of her friends.
Bindi Nicholls, 50, told London's Southwark Crown Court that her friend revealed to her that she had a consensual affair with her father from the age of 18 or 19.
But she said the alleged victim never told her that her first sexual encounter with Harris was when she was 13, and also dismissed claims that Harris sexually assaulted her friend while she slept in the same room as "sort of laughable" and "ridiculous".
The woman, who is one of four who claim the veteran entertainer indecently assaulted them, has told the court that he first groped her on holiday in the 1970s, when she was 13, and that on one occasion he assaulted her while Bindi slept in the same room.
The star, who lived in Sydenham during the 1960s and 1970s, has admitted having a relationship with the alleged victim, but says it was consensual and began only when she was 18.
Harris faces 12 counts of indecent assault - seven relating to his daughter's friend - on four women between 1968 and 1986.
Today Mrs Nicholls described her shock when the woman told her she had been having an affair with her father.
She said she confided in her friend that she suspected her father of having a sexual relationship with a woman who was living in an annexe at the family home, sparking an "odd" reaction from her.
"It felt like she was in love with my dad, which was just weird," she told the court.
The reaction prompted her to ask the woman if something had happened between her and Harris, she said.
"She said 'Well, it's been going on since I was 18 or 19, Bindi, it's been going on for ages'."
Describing how she felt a "head rush" at the time, she said: "The shock was just appalling."
Breaking down, she described her reaction as "utter shock", saying: "It was just horrible.
"It felt like the whole world had changed in an instant."
But she denied the woman's claims that it had been going on since she was 13, saying: "No, she never said that."
Mrs Nicholls said she later confronted her father over the phone about the affair.
"I rang him up and said 'What on earth has happened here, you have had an affair with my friend, how dare you, how could you, it's my best friend'.
"I was just so angry with him. I said how long has it been going on for, he said it was in Bray and he said 'Sorry, sorry love, I'm so sorry'.
Asked if she had worked through the issue with her father, she told the court: "I realise we are all human. I think I had had him on a pedestal and now I can see him as a father and a man."
Earlier Mrs Nicholls dismissed the alleged victim's claims that Harris performed oral sex on her while his daughter was asleep in the same room as "laughable".
The 50-year-old, who wore a pink cardigan and black pencil skirt, laughed as she dismissed the claim as "ridiculous".
She said: "No, it's sort of laughable. There's no way I would fall asleep and have someone in the bed next to me doing stuff.
"That's ridiculous, it really is."
Harris remained impassive as his daughter took to the witness box, occasionally drying her eyes with a tissue.
Mrs Nicholls' evidence came after the veteran entertainer was forced to deny that he deliberately lied to the jury when he claimed he had never been to Cambridge until a few years ago.
The jury was shown footage of the star appearing in a TV game show Star Games filmed in Cambridge in 1978, despite Harris saying he had not visited the city until three or four years ago.
Harris denied deliberately lying, saying that he had forgotten appearing in the programme until he was shown the video, and was not aware at the time that he was even in Cambridge.
As she took to the witness box after her father, Mrs Nicholls broke down as she described a "turning point" in her relationship with her friend.
Mrs Nicholls, who earlier described the girl as her "absolute bestest friend in the world", broke down in tears as she said their friendship changed when the Harris family moved house to Bray in Berkshire.
"We were devastated, both of us," she said through tears.
When they were children, she loved the girl "to bits", she said, and said they saw each other "all the time, as much time as I could" and would "chat, chat, chat".
Mrs Nicholls described her mother Alwen, who has been in court supporting Harris throughout his trial, as "lovely, soft and gentle", but of her father, she said: "Dad didn't really take much notice of me, or anyone for that matter, at home.
"I think when he is out in the world he wants to give everyone his time and everyone is new and he can tell new jokes and new everything.
"But when he is at home he is very much switched off, very quiet, quite often working, making something."
Mrs Nicholls, who the court heard is an only child, said she "travelled the world" as a child but was often "incredibly lonely", so was overjoyed when her friend joined the family on a holiday. She said they "literally were stuck together like glue".
The court has heard that the alleged victim claims she was first assaulted by Harris in her hotel room during that holiday.
Of a claim the girl has made that Harris groped her as he wrapped a towel around her on the beach, the star's daughter told jurors that him wrapping a towel around her friend would be "odd".
"You put towels round people who are little when they come out of the water.
"It would be strange, really odd, my dad wouldn't do that anyway. I can't see that happening, not at all."
She said her friend was "incredibly independent" and there was "no way" anyone would dry her down.
She told the court: "My dad doesn't like going on the beach anyway, so I can't imagine him even being on the beach. He hates sunbathing."
Under-cross examination by prosecutor Sasha Wass QC, Mrs Nicholls was asked if she was trying to help her father with her evidence.
"This isn't about me helping my father, this is about telling the truth," she said, and denied a suggestion that she and her father had colluded over their evidence.