But this charming and amicable side hid another dark side, the jury of six men and six women was told.
The artist and singer was "a Jekyll and Hyde character", Ms Wass said.
"This hidden side is what this case is about - and it is known only to Harris and those he molested."
No-one screamed or shouted or told an adult at the time.
"Harris was too famous, too powerful, his reputation made him untouchable," Ms Wass told Southwark Crown Court.
Many assaults were "brazen".
The court heard that Harris knew children were in awe of him.
"You will see a pattern during this case of Mr Harris approaching girls in a purely friendly way and then, once he is in close physical contact with them, taking advantage of the situation in order to indecently assault them," Ms Wass said.
Witnesses would tell the court they didn't complain at the time because they thought no-one would believe them.
However, an older TV make-up artist in Australia has said that to those in the know, Harris was referred to as "the octopus" because of his roaming hands.
The court heard one of the four main complainants was a close friend of Harris's daughter, Bindi, who joined the family on an overseas holiday in the late 1970s.
It was in Hawaii that Harris allegedly abused Bindi's friend for the first time after the then 13-year-old had taken a shower at their hotel and was wrapped only in a towel.
"Mr Harris came into (her) bedroom and gave her a hug and then pretended to tickle her," Ms Wass told the court.
"Mr Harris, having made physical contact with (her) on the pretext of a hug and a tickle, then wrapped his hands around her and put his hands inside the towel."
Ms Wass said Harris again indecently touched the 13-year-old - who the family had known for more than a decade - on other occasions in Hawaii and then in Australia.
When the victim returned to London after the holiday she started drinking and within a few years was a full-blown teenage alcoholic.
Ms Wass said the victim was subsequently abused by Harris over the next 15 years.
"Harris groomed her like a pet on that trip", the prosecutor said, adding that by the time Bindi's friend was in her 20s she effectively did whatever the entertainer said.
The complainant herself has said it was like she was his "little toy". Ms Wass said the victim eventually told school friends about the abuse and, later, medical professionals in the 1990s when she was in her 30s.
In 1997, Harris himself wrote a confession letter to the complainant's father, the prosecutor told the court in her opening address.
But while Harris admitted having sexual relations with the man's daughter the note was a "confess and avoid" letter.
Ms Wass explained that was because it avoided admitting anything happened when the alleged victim was underage.
The prosecutor said the 1997 letter was akin to former US president Bill Clinton admitting to smoking cannabis, but insisting he hadn't inhaled.
Harris apologised to the victim's father but said a consensual relationship only took place once the complainant was over the age of consent.
"When I see the misery I have caused (her) I am sickened by myself," Harris wrote in the letter which was read out in court.
Ms Wass said Harris had effectively "nailed his colours to the mast" because the defendant couldn't now say Bindi's friend had invented the entire story.
Harris watched Friday's proceedings from a glass-walled dock inside the court. He listened with the aid of a hearing loop.
Earlier, the veteran entertainer arrived at court holding hands with his wife and daughter.
Harris was wearing a grey suit, pale pink shirt and multi-coloured tie.
The trial, expected to last until the end of June, continues.
- AAP
