Peter Wolffsohn was two years old when he had a stroke.
His parents thought he was having a tantrum but over the following day they realised something else was wrong.
He was not speaking very much, he was not settling to any activities and he was not holding his cup properly.
So they took him to their GP and after extensive tests, including an MRI scan, they were told he had had a stroke - a condition normally associated with older people.
Yet research shows that at least 400 children and babies have a stroke each year in the UK.
Once the immediate symptoms of the stroke had passed, Peter was diagnosed with permanent hemiplegia, a paralysis of the arm, leg and trunk on one side of his body.
"I thought it would just all come back," says his mother, Rachel, of the limb movement and speech which Peter lost that day.
Doctors discovered Peter had narrow arteries so he was put on warfarin for six months and kept in hospital for three weeks. He now takes aspirin every day to help thin his blood.
Five years on and Peter is a bright, happy boy who has regained his speech and enjoys going to school - but he still needs help and support with many aspects of daily life.
"He manages things fairly well," says his mother. "In school he as one-to-one support and at home I have to help him with anything that requires two hands, like cutting up his food and washing himself."
"He wears a splint on his foot and a lycra splint on his arm. If we don't keep his foot, ankle and lower leg in line then he can get quite twisted and might need surgery in the future."
Rachel has long-term worries about his hips and knees because his foot is being pushed into an odd shape by the hemiplegia.
And Peter's right hand can become a clenched fist, particularly when he's concentrating on something.
So Peter has lots of physiotherapy to help take away the tightness in his muscles. Part of his physio treatment also entails botox injections which act as a muscle relaxant.
"It's all about helping the brain to retrain the muscles," explains Rachel.
Hemiplegia is caused by damage to some part of the brain, which may happen before, during, soon after birth or later in childhood.
Injury to the left side of the brain will cause a right hemiplegia and injury to the right side a left hemiplegia. This is a condition much less well known than cerebral palsy - which has similar physical manifestations - and yet one in 1,000 children live with the condition.
Dr Jean-Pierre Lin, consultant paediatric neurologist at Evelina Children's Hospital in London, says that in children the commonest cause is damage to the foetal brain during pregnancy which means that the brain does not develop in a normal way.
"Parents may notice their child's movements are progressing differently from other children's or that they are not occurring at the right times," he says.
During childhood, hemiplegia is often caused by a stroke, like Peter's, when a bleed or clot damages part of the brain.
"You can get acute strokes in children just as you do in adults," says Dr Lin.
"What's important is recognising them as strokes. We need grass roots vigilance of strokes because that's where the diagnosis will be made."
Peter's diagnosis was made within 48 hours but Dr Lin worries that strokes are generally under-recognised in children. Any delay in treating and managing their rehabilitation could be crucial, he says.
Although hemiplegia cannot be cured, the charity HemiHelp's website says a lot can be done to minimise its effects - and much of that through play-based activities.
"As they get older, many children and young people with hemiplegia can be encouraged to develop better use of their weaker side through involvement in their chosen sports and hobbies."
Other side effects of hemiplegia can include epilepsy, visual impairment or speech difficulties. And some children may develop specific learning difficulties or emotional and behavioural problems.
In Peter's case, the focus is all on therapy which uses his muscles and does not let them tighten up, but this isn't always easy to arrange.
"Many parents don't get all the support they need to give their child the best opportunity of living a full life," says Alice Doyle from HemiHelp.
At her son's school, however, Rachel is pleased with the support he has received.
"Peter has an amazing PE teacher at school who has asked lots of questions about what he can and can't do. He also makes sure the children don't pick teams and Peter is left to the end, for example," says his mother Rachel.
And Peter is happy to tell people that he's had a stroke.
"He has never known any different really," says Rachel. "People often ask him what he's done to his arm, which he gets a bit frustrated by, but it's just people being curious."
Rachel hopes Peter will be able to live an independent life when he's older, but she knows it is not straightforward. There will be difficulties.
But this is one brave boy who is not about to have a tantrum over it.