Researchers in the British city of Nottingham say the cloned siblings of Dolly the sheep are in good health raising hopes that the process doesn't effect physical wellbeing. The four cloned sisters have just passed their ninth birthdays. Dolly who had to be put down in 2003 had aged prematurely because she developed osteoarthritis at a relatively young age. Here is our science correspondent Jonathan Amos.

Dolly's birth was a sensation, the first genetic copy of a mammal made from a cell taken from an adult sheep. It was how it is a way of developing new medical therapies or to save endangered species. But cloning is very inefficient. Most attempts fail and even in Dolly's case, she had a lung disease and painful joints. Scientists wondered if that was because her genetic clock had not been reset properly.

That possibility has now been tested in four sheep cloned from the same cells as Dolly. They are her genetic sisters called Debby, Denis, Dianna and Daisy. They are now nine, older than she was but don't show the same degenerative issues. Claire from Nottingham University says this finding renews hope in the promise of cloning but concedes the process is still too inefficient.

And so there still remains an ethical and welfare concern with cloning. And what we have to do is to reduce the incidents of theses losses and the severity of these losses before I think the technique will be widely accepted by the general public.

The scientists who report their studies in the journey Nature Communications say it's been fascinating to work with animal copies. Some do develop quite different personalities. But they are virtually impossible to tell apart.

That report from Jonathan Amos.

It seems to have been around for quite a while that this weekend after two months of previews, we will see the gala opening in London of Harry Potter and the Cursed Child. It's described as the eighth Potter story. But the critics have been allowed in ahead of the official opening and the reviews are now in the newspapers. So what's it about? A question for our arts correspondent Vincent Dowd.

It's a five-hour epic in two parts so I can't say much about it. And of course I'm not really supposed to say that much about it anyway. There is a lot in it basically set 19 years after the end of the novels or the films. Harry played now by Jamie Parker is 37.

What have the critics made of it all so far?

They have loved it. I think without exception. I'm not sure I can remember reviews like this since the producers are in New York. Just one or two quotes, The Times, "It's the real deal live in front of you, so much better than any film could be".