John Challis, best known as Boycie in Only Fools and Horses, has called Roger Lloyd Pack "remarkable" and "irreplaceable":
I spoke to Roger two days ago.
Roger said it was a bit awkward to talk at that particular moment. It is very sad and very distressing.
My thoughts are with his family. He was a remarkable man and he'll be missed.
Roger is irreplaceable. It's a very sorry day.
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Mr Kim has made two recent visits to China.
The study looked at the development of 422 children over the course of eight years.
The president said they will come into force if China refuses to change its practices.