Singer Jurie Els tried to deal with young Robbie Klay's "sex obsession" by explaining to him what normal behaviour was, Els told the High Court in Pretoria on Friday.

Els, on trial for allegedly sexually molesting Klay as a child, testified he was "shocked" about Klay's obsession with sex when he met him for the first time at 11.

"He talked openly about graphic sex scenes in movies. In time it became worse and Robbie started talking about sex more and more. I realised it was a big issue for him," Els said.

"He would for example make dreadful, hard-core sex references in front of his mother, which shocked me."

Els said he often talked to Klay to explain what acceptable norms were.

"As he reached puberty, it became worse. As a teacher I knew most teenage boys have a type of sex obsession."

Els said Klay's sexual promiscuity, immorality and the vulgar expressions had offended him as a Christian.

He admitted to on occasion sharing a room with Klay after concerts and having a very close bond with the young singer.

But it never occurred to him that this could one day become a problem, Els said.

"Just like a father sharing a room with his son, it never occurred to me that he would years later accuse me of molestation."

Klay's mom's breast enlargement

He revealed he had to look after Klay on several occasions when Klay's mother, Jenny Liebenberg, went to hospital for a breast enlargement operation.

Prosecutor Corlie Bouwer remarked that Liebenberg seems to have recovered well.

"Yes, beautifully," Els replied.

He said the impression that Klay only caused problems and drama in his life was wrong, as he and Klay had shared many good times when Klay was like a son to him.

This was why he had repeatedly forgiven Klay for his "lies and deceit".

"He was a friend. I had a soft spot for him. He has a wonderful personality and great talent," Els said.

He said his final fall-out with Klay came because his wife Hestrie was made of sterner stuff than him and "did not take any nonsense".

He and Hestrie had confronted Klay about his lies and had taken back his car.

At the time, he thought Klay's threats of revenge had been directed at Hestrie because he knew she had persuaded Els to take a stand.

The trial will continue on Monday.