A "freak combination of circumstances" for which no one was to blame led to a Northern Ireland man falling out a window at a friend's house, the High Court in London has heard.
Blind adventurer Mark Pollock, from Co Down, is suing Enda and Madeline Cahill for millions of pounds after falling 25 feet onto the patio of their home in Henley during the town's regatta in July 2010.
The 39-year-old was staying with the Cahills, who were good friends, when he fell through the window of his upstairs bedroom, suffering severe spinal injuries.
He previously told the court he was probably "on his way to the bathroom and was disorientated and tripped out the window".
The accident left him paralysed and he has to use a wheelchair and is dependent on care.
His legal team, led by Christopher Wilson-Smith QC, blamed Mr and Mrs Cahill for the accident and said that the window should never have been left open.
But the Cahills, of Woodview, Remenham Lane, Henley, deny the accident was their fault.
Stephen Grime QC, for the Cahills, told the court it was a "very unusual, most unhappy case". He urged Mr Justice William Davis to bring a "large injection of common sense" to bear and dismiss Mr Pollock's claim.
"We say this was a freak combination of circumstances which no person would have foreseen and for which no one can or should be blamed," he added. "To reach a contrary conclusion does require an extensive use of hindsight."
Martin Murphy, who shared the bedroom with Mr Pollock, had told the court: "We were sharing a room in hot weather, so I'm sure we opened the window."
Mr Grime described it as an "ordinary room and ordinary window". "There is nothing in the slightest degree abnormal about the window or its dimensions or its situated position in the room," he added.
"Why should either Mr Pollock before the accident, or Madeline Cahill or Enda Cahill, have thought the window was a risk to him?"
The QC also told the court it was '"not fair to say that Mrs Cahill ignored the risk".
"She did not perceive the window as a risk - she can't be blamed in any way," he said.
In the light of expert evidence, Mr Grime queried Mr Pollock's theory that he was disorientated, slipped and fell out of the window.
The Commonwealth Games medal winner himself has told the court that he has no memory of the accident.
Mr Grime said other possibilities were that he had leaned out of the window or even that he had been sleepwalking. Neither of those would involve negligence by the Cahills, he told the judge.
Mr Pollock, the first blind man to race to the South Pole, lost his sight in 1998 at the age of 22 but went on to win bronze and silver medals at the 2002 Commonwealth Games.
He has also taken part in extreme marathons and Ironman events and, not long before the accident, in June 2010, he completed the 1,400 mile Round Ireland Yacht Race.
The hearing at the High Court continues.