Mr Sharples said he climbed on the bus taking the dignitaries to view the body at the Union Buildings in Pretoria and he had sat at the back of the bus.
He saw Bono and Campbell looking for a seat so shouted to them: "Down here, there's lots of seats."
He said the two stars came down to the back of the bus and someone suggested Campbell sit on Dr Sharple's knee.
"I thought they were being serious, but she sat down besides me."
"We had a good old chat. She is very gorgeous and has a groovy voice," Dr Sharples said.
Campbell had never been to New Zealand but had heard all about it. He said Bono loved New Zealand.
However, the light hearted moment did not take away from the seriousness of the occasion.
Dr Sharples said Mandela looked at ease.
"It was the opportunity to do a traditional thing to a great man."
He said he had performed a poro poro aki, which is a traditional Maori farewell for the dead and that he had done it on behalf of Maori people and New Zealand.
Labour leader David Cunliffe, who was with Dr Sharples at the time, said it had been a very sombre time and the dignitaries had filed past silently.
He said Mandela was dressed in one of his famous shirts.
"He was looking like a big man at rest," Mr Cunliffe said.
