The father of a seven-year-old girl chased a bouncy castle as it blew "30 to 50ft in the air" and rolled down a hill with her inside, a court has heard.
Lee Grant heard a scream and told onlookers "my daughter's in there" after seeing the inflatable lift into the air, hit a caravan and flip over at Harlow Town Park in Essex, Chelmsford Crown Court was told.
Fairground worker William Thurston, 29, and his wife, Shelby Thurston, 26, are on trial accused of manslaughter by gross negligence and a health and safety offence over the death of Mr Grant's daughter Summer.
Opening the prosecution case, Tracy Ayling QC said the youngster and her family visited Thurstons Fun Fair on Easter Saturday in 2016, and that Storm Katie was expected to arrive by Easter Monday.
"The weather was cold and windy," Ms Ayling said.
"Summer was playing in a bouncy castle that was one of the fair's attractions run by these two defendants.
"While Summer was in the bouncy castle, it blew away from its moorings, bounced 300 metres down a hill; having hit a tree, it came to rest."
Ms Ayling said Summer's father heard a scream and ran after the bouncy castle but it was moving too fast for him to catch it.
"He turned and saw that the dome inflatable had lifted into the air, appeared to hit a caravan before flipping over," the prosecutor told the court.
"He said 'my daughter's in there'."
Mr Grant told the court he heard his mother scream "no" and within seconds the bouncy castle blew away.
"I remember it blowing over some sort of caravan and kept on going over the field," he said.
"I started running after the bouncy castle down the field."
He continued: "It was 30 to 50ft in the air and just rolling down the field, just rolling and rolling.
"I think it hit a tree. At the end of the field, it came to a halt when it hit the fence.
"I couldn't find her. I couldn't find the entrance to the bouncy castle as it had deflated by the time it reached the end."
Witnesses described seeing the bouncy castle "cartwheeling in the air" and "cartwheeling down a hill" before it came to a stop.
Ms Ayling said Summer was found inside the inflatable and taken to hospital but died from her injuries.
The prosecutor told the court that the Thurstons "breached the duty of care they owed to Summer Grant".
She accused the two defendants of failing to ensure that the bouncy castle was "adequately anchored to the ground" and failing to monitor weather conditions to ensure it was safe to use.
Mr Thurston was among those who chased the bouncy castle as it blew away and found Summer "very badly injured and struggling to breathe", Ms Ayling added.
Mr and Mrs Thurston, of Wilburton, near Ely, Cambridgeshire, both deny the charges against them.
The trial continues.