Specialist surgeons at Great Ormond Street Hospital today began an operation to separate the conjoined twins born to a Shropshire teenager.

The operation to separate Hope and Faith Williams was brought forward after concerns developed over the health of the twin girls last night.

The babies, born to Laura, 18, and Aled Williams, 28, of Harlescott, Shrewsbury, were delivered by Caesarean section last Wednesday at University Hospital, London.

They were immediately moved to Great Ormond Street and talks were due to take place today about the specialist surgery required to separate the girls, who are joined from the breast bone to the navel. Hayley Dodman, spokeswoman for Great Ormond Street Hospital, said: “The separation of conjoined twins Faith and Hope Williams has been brought forward and is currently taking place, after some concerns developed last night.

“Obviously, the final decision about separation surgery was made by the family.

“Laura and Aled Williams would like to thank all the hospitals involved in their care for everything they have done for the family so far, in particular, the surgeons and other staff who are currently in surgery conducting the separation.”The complicated surgery is being carried out by a specialist team led by Professor Agostino Pierro, who is one of the most experienced surgeons in the field.

Great Ormond Street Hospital is the most experienced centre in Europe for the management of and, if necessary, the separation of conjoined twins.

Doctors at the Royal Shrewsbury Hospital had warned Mrs Williams and her husband Aled that the twins might not survive after a 12-week scan revealed that they were joined.

But the couple, who live with Laura’s mother Wendy Rackham, refused to have a termination.

The team at the hospital refer to three sorts of cases; planned separation, where the children are stable and where separation can be attempted when the children are not newborns, emergency separation where one or both children are dead or dying and therefore surgeons are seeking to give one child a chance of survival and inoperable cases.

In general children joined at the heart are inoperable and, sadly, will usually die.

Miss Dodman added that success for planned separations carried out at Great Ormond Street is more than 80 per cent.

Conjoined twins occur when the single egg from which identical twins develop fails to divide properly after conception.

It usually happens in women 25 to 40 years old but is so rare it only happens once in every 200,000 births.

The survival rate is somewhere between five and 25 per cent.