Luke had been excluded from school on the day that he died

The 16-year-old told Cardiff Crown Court that the bus had moved off with Luke Tanhai hanging on to the outside.

He said Luke was smiling as he held on the rail of the double-decker outside Cardiff High School.

Colin Haynes, 59, of Gabalfa, Cardiff, denies a charge of causing death by dangerous driving. The case continues.

The teenager told the court via a video link: "The bus picked up speed then slowed down for a roundabout.

"One of my friends jumped off - I looked and saw him running as he landed.

"I looked straight at Luke, he was smiling at me. I said, 'jump off the bus,' but he just smiled at me and wouldn't get off.

"I jumped off and by this time the bus had gone round the roundabout and was getting faster.

"When I got off I shouted 'get off the bus' to Luke, but I think he was a bit scared to jump off."

Mr Haynes told police he was not aware of Luke outside the vehicle

The boy told the court he started running after the bus but did not see how Luke fell or jumped to his death.

He said: "We started running down the street and the next thing we knew he was on the floor with blood around him."

The boy added: "There was something wrong with that driver. Why didn't he stop?

"He acted like no-one was there."

The teenager told the jury Luke had been trying to get on the bus but did not have the fare.

He said: "The driver wouldn't let Luke on the bus, we were just standing there - all the kids were standing in the entrance by the door to the bus.

"The next thing I knew the bus starts going with me, Luke and another boy holding on to a pole."

The incident happened as pupils were leaving Cardiff High School in the Lakeside area in September 2003.

He died from head injuries, possibly caused by the back wheels of the double-decker bus.

Peter Heywood, prosecuting, has told the court Mr Haynes was driving the vehicle dangerously because he was aware three boys were clinging to the outside of the vehicle.

Mr Heywood also said that during police interviews Mr Haynes claimed he was not aware of Luke outside the vehicle.