A 13-year-old boy who died in a crash involving a £1.2 million Ferrari jumped into the supercar "in a flash" when a businessman offered to take him for a "spin", a court has heard.
Matthew Cobden, of Long Lodge Drive, Walton-on-Thames, Surrey, is on trial at Winchester Crown Court accused of causing the death by careless driving of Alexander Worth in an accident involving a Ferrari F50 on August 22, 2016.
Justin Smith, the partner of the mother of teenager Alexander, said that he was delivering a battery to the car storage business run by Cobden at North Warnborough, Hampshire, when the accident happened.
He said that Alexander and the boy's mother, Arabella, from Kingsworthy, had joined him after they had spent the day in London.
In a statement read to the court, Mr Smith said that 39-year-old Cobden showed them around his premises.
He said: "He was pulling off the covers to show Alexander the cars, including an Aston Martin."
Mr Smith said that a truck with the Ferrari and a silver Porsche arrived.
He said: "Alex told me that the Ferrari was his friend's favourite car and I said that I would see if Matt minded him taking a photograph.
"Matt replied 'I could take you for a spin'.
"In a flash, Alexander dashed around the Ferrari and got into the passenger's seat. I thought about the seatbelts and was pretty sure that Arabella had shouted out to them.
"The car roared off whilst myself, Arabella and Matt's dad stood around. We couldn't see anything of the vehicle after it had pulled away due to the hedges.
"I heard the roar of the engine and some revving. This was followed up with a bit of a bang. Arabella asked 'Do you think Alexander is ok?'
"We then started to walk faster and jog up around the hedge.
"It was at this point we heard a distressed shout of 'Dad' from Matt."
He said that they drove to the crash scene and found Alexander "on his back motionless" and Matt was saying "I'm so sorry, I'm so sorry".
Mr Smith said that the farm owner, Duncan Janaway, then arrived and called 999 and gave Alexander chest compressions.
Mr Smith added: "I think any one of us would have got in the car that day. Matt was doing a lovely thing and the plan was for him to drive out, down the lane and back."
The jury were later being taken for a visit to the location of the crash at the farm entrance road to walk the route taken by the Ferrari.
The trial has heard that the Ferrari hit a fence post at the side of the road which launched it into the air, flipping it and turning it round 270 degrees.
Both Cobden and Alexander were not wearing seatbelts, the court has heard.
Cobden denies the charge and the trial continues.