A teenager left brain-damaged after a heart operation 15 years ago has told of her relief after winning a compensation deal worth millions of pounds.

Ella Blake, 16, of Clifton Place, Brighton, suffers from impaired emotional development and co-ordination after heart bypass equipment was wrongly used during a common operation to mend a hole in her heart in March 1991.

It resulted in an air embolism and Ella now requires constant care and support in her daily life.

Her mother, Dawn, 44, has fought a long battle with London's Great Ormond Street Hospital which culminated in a deal being reached in the High Court yesterday. The authority admitted breach of duty but disputed that all of Ella's injuries could be attributed to the flawed operation.

Ella said: "It's a relief it's all over. It's been so long and I felt it would never end."

Ella's father is not in regular contact with his daughter and her mother, Dawn, has relied on friends for support during the ordeal with the National Health Service Litigation Authority (NHSLA). She said: "It's been an emotional rollercoaster. I have learnt so much from the families and children I have met as a result of this and I have met strangers who have become angels, providing fantastic support.

"But it has been hugely challenging and there have been times I have felt very close to the edge, thinking I could not cope any more. It has taken me to the extremes of myself."

She said when Ella first came out of the heart operation in 1991, doctors told her to prepare for her death.

But after relying on machines to keep her alive for two months, Ella began to make progress and nurses dubbed her "the miracle baby".

Despite her enormous strength of character and personality, Ella's brain damage meant she was six years old before she stopped wearing nappies and, angry with her own shortcomings, would hit her head and call herself a "durrbrain".

Dawn compiled a thick binder of documents for her legal team which outlined the emotional, social and physical problems she believes were directly caused by the hospital's failings.

The NHSLA's barrister, Philip Havers QC, yesterday publicly apologised to Ella's family, adding that his clients "greatly regret what occurred".

Mr Justice Gray approved a settlement which guarantees Ella a payment of £500,000, plus annual payments of £23,000, index linked for as long as she lives. The judge also paid tribute to Dawn for the care she has lavished on Ella over the years, commending her "enormous devotion".

It was only her mother's commitment that ensured the case was seen through to the end and "not settled at a fraction of what the claim was worth", the judge said.

Dawn plans to use the lump sum to buy an apartment for Ella but said they are looking forward to a trip to draw a line under the past 15 years.

She said: "This means Ella can live independently with a mentor to help her living skills."

Ella is soon to leave her special needs school, Patcham House, to attend Lewes College.