* Rolf Harris was huge star in Britain, Australia
* One of his victims abused for 16 years
* Inquiry launched after death of BBC presenter Jimmy Savile (Adds quotes, background)
LONDON, June 30 (Reuters) - Rolf Harris, a mainstay of family entertainment in Britain and Australia for more than 50 years, was found guilty on Monday on 12 charges of indecently assaulting young girls over two decades.
Harris, 84, was unanimously convicted by a jury of six men and six women of sexually assaulting four girls, some as young as seven or eight, between 1968 and 1986.
An artist and musician who presented prime-time TV shows mostly aimed at children, Harris is the biggest name to go on trial since British police launched a major investigation after revelations that the late BBC TV host Jimmy Savile was a prolific child sex abuser.
"Rolf Harris used his status and position as a world famous children's entertainer to sexually assault young girls over a period spanning 18 years," Jenny Hopkins, Deputy Chief Crown Prosecutor in London, told reporters.
"The victims in this case have suffered in silence for many years and have only recently found the courage to come forward."
During the trial, the prosecution had portrayed the bearded, bespectacled entertainer, who once painted Queen Elizabeth's portrait, as a predator who groomed and abused one woman for her entire teenage and young-adult life.
The London court was told he first assaulted the woman when she got out of the shower aged 13, and then repeatedly abused her until she was 28 years old.
"You were able to play with her like she was a toy," prosecutor Sasha Wass told Harris, commenting that beneath his friendly loveable exterior there was a "darker side lurking".
"Everybody in this court who has given evidence has said that they wouldn't have stood a chance against you if it was your word against theirs. Because you were so famous, so popular, so loved by everyone," she said.
Harris had denied all the charges and said the allegations against him were "laughable". He said the girl he abused for years had invited his sexual advances, leading to a consensual affair.
During his appearance in the witness box, he even sang a brief extract of his comedy song "Jake the Peg", mimicked the sound of a didgeridoo - a long, tubular Aboriginal instrument - and mimed his invention of the wobble-board, an instrument he made famous in the 1960s.
His wife Alwen had been in court to hear the allegations against him, but a spokesman for the Harris family said they would not be commenting on the verdicts.
Harris is one of more than a dozen ageing British celebrities to have been targeted by police as part of the same over-arching investigation, named Operation Yewtree, which was launched after the revelations about Savile emerged.
In 2012, London police said Savile, one of the Britain's best-known celebrities in the 1970s and 1980s, had abused hundreds of victims, mainly youngsters, at hospitals and at BBC premises over six decades until his death aged 84 in 2011.
Some of those under investigation complained that Operation Yewtree had become a witch hunt, but in May it led to the jailing of Britain's best-known showbusiness publicist, Max Clifford, for indecently assaulting teenage girls some 30 years ago.