A British girl, who was given an extra heart as a toddler, has become the world's first heart transplant patient to make a full recovery after having her donor organ removed and function restored to her original heart.

Hannah Clark, now 16, had a "piggyback" transplant operation in 1995 aged two, when a new heart was inserted in parallel to her own failing one.

The donor organ had to be removed three-and-a-half years ago because the immunosuppressant drugs she was taking to avoid organ rejection caused cancer - but by then her own heart had recovered sufficiently to work on its own.

Since the surgery, which took place in 2006, Ms Clark has made a full recovery from the cancer and has a normal cardiac function, her doctors have said.

"Now we are a lot more confident (about this procedure)," said Magdi Yacoub from Imperial College London, who co-led the surgery team.

"The heart muscle itself, which was not doing anything at all, has recovered."

He added cardiomyopathy, or the deterioration of the function of the heart muscle, was relatively common in children in the first year of their life.

Victor Tsang from Great Ormond Street Hospital, who was the other surgery team leader, said Ms Clarke's case offered hope for other patients with heart failure.

"Hannah's case highlights that in cases of cardiomyopathy such as hers, it is possible for the patient's own heart to make a full recovery if it is given adequate support to do so," Mr Tsang told reporters.

Her case study was reported in the Lancet medical journal.

Ms Clark, who was forced to take 16 different drugs at one stage to control her illness, burst into tears when a journalist asked her to relate how her life has changed with the surgery.

She said she was cherishing every moment and now has a Saturday job working with animals. "Thanks to this operation, I've now got a normal life just like all of my friends."

Her mother Elizabeth Clark said: "She doesn't think about tomorrow, she thinks about today. She wakes up smiling every day."