The father of a 13-year-old schoolgirl with a weak heart who died after falling ill during a PE lesson has told how his beloved daughter spent her life battling with her condition.

Tragic Sasha Bartin was warming up for a hockey match at Westfield Community School in Yeovil when she began to feel unwell. She was taken ill and later died in hospital.

In a tearful interview from his Yeovil home yesterday, her father Glynn Cooper, 34, told how his daughter had led a happy life despite the condition. She was due to be operated on after turning 18.

"She had been doing this for years and lived a perfectly healthy life," she said.

''I used to watch her play football and she could usually keep going happily until a break at half-time. But something must have been wrong on that day.

''To everyone else she looked like she had a normal life but we always knew she was ill.

''Her GP said that when her chest hurt or when she got out of breath she should stop what she was doing."

Manchester United fan Sasha was born with a narrow heart valve and underwent corrective surgery at Bristol Royal Infirmary aged just two weeks.

But the operation was not a complete success and Sasha was left needing further surgery to correct the defective valve.

Doctors feared further treatment while Sasha was still growing could lead to more problems, and were waiting until she was 18 before they operated again.

She underwent regular check-ups at Bristol Children's Hospital and with her GP and was even able to take part in moderate exercise.

Mother Katrina Bartin, 37, added: ''I'm devastated. It was just such a shock. She seemed fine on Monday morning.

"She was a wonderful girl with lots of friends. I can't believe she's gone."

A post-mortem examination will be carried out at London's Great Ormond Street Hospital.

Mr Cooper added: "She brightened up everyone's day and was smiling all the time. I have never seen her unhappy, if I was upset she would cheer me up by making me laugh.

''I could not have asked to have a better daughter – she was like my best friend.

"She was a smiling angel who brightened up the lives of everyone she came into contact with. I will miss her so much."

Siblings Naomi, 16, and Lewis, 11, added: "Sasha, I miss you so much already, you will always been my baby sister and there is not one day I will not remember you, your smile, your bright eyes.

''I love you so much. I have been thinking of a reason why you have gone and I have to figure it's because they need someone up there to show those angels how to do it."