When throwing a ball for a restless dog during the daily walk, it would never cross the owner's mind that this could result in a lawsuit and an up to £50,000 payout.
However, this was the case for investment banker Carina Read, who merrily chucked the toy for her cocker spaniel, Felix as she walked through Acton Green Common, West London.
The dog then ran into the path of 70-year-old publishing boss David Crane, who flew over the handlebars of his bicycle and onto the floor. The collision caused a brain haemorrhage. The court heard that his injuries have resulted in him suffering from loss of memory and concentration as well as headaches.
His lawyers told Central London County Court the 48-year-old dog owner was negligent in failing to properly control Felix, who should not have been allowed to stray into Mr Crane's path.
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While Ms Read denies all responsibility and has labeled the March 2016 incident a "freak accident", the injured septuagenarian won his bid and will be claiming the payout.
The banker said Felix only ran in front of the bike because he was "stunned" after the thrown ball hit him on the head.
She also claimed Mr Crane was going too fast and should not have been riding on the path as it was out of bounds to cyclists in line with local bylaws.
Ealing Council's byelaws state that no person shall, without reasonable excuse, ride a cycle in the park, except in any part of the ground where there is a right of way for cycles.
"Cycling is prohibited without reasonable excuse on Acton Green Common but the council chooses not to enforce as it supports considerate cycling in parks," a spokesman for Ealing Council said.
Judge Patrick Andrews has now ruled that Ms Read was negligent, having failed to call back Felix as he shot towards the path and the oncoming cyclist.
"After considering all the facts and evidence, I find that on balance of probabilities, in failing to call back Felix, which she clearly had time to do, Ms Reid exposed Mr Crane to risk of injury," he said.
The ruling means Mr Crane, who claimed up to £50,000, is entitled to a damages payout, with the amount due to be assessed at another hearing.
The publisher said that he has been cycling around London for 40 years without incident and he was unable to avoid the dog as the accident occurred in a "split second".
He denied claims that he was hurrying to get to work on time or that he was riding too fast, telling the court that he was incapable of speeding along on his bike because he had weighed 18 stone at the time.
Mr Crane, who declared himself "100% a dog lover", said outside court that he has now taken to walking friends' dogs for exercise as he can no longer ride his bike or enjoy skiing.
Ms Read's barrister Nigel Lewers told the judge that when she threw the ball for Felix the path was clear, but that the ball bounced off the dog's head as he chased it, deflecting it towards the path.
"At that point, she became aware of Mr Crane cycling at speed with his head down," he added.
"She tried to warn him, but Felix chased the ball across the path and was struck by the front wheel of the bicycle.
"She was doing what she and no doubt many others had done in the same or similar areas of the common - throwing a ball for her dog down an open strip of grass and not in the direction of the path."
He argued that such dog walking was a "way of life" for people in the local area.
But giving his ruling on the case, Judge Andrews found that Ms Read should have done more to keep Felix in check.
The dog should have been warned and called back, he said, also questioning whether it was safe to have thrown the ball when Felix was so close to the path.
Ms Read had insisted in evidence that Felix was a "well trained dog who returned when he was called", noted Judge Andrews, concluding that she had not called the dog back and so was liable to pay damages.
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