Professor Roger Williams, who has been in charge of Best's treatment since he underwent a liver transplant in 2002, said: "Quite what will happen over the next 24 hours is difficult to say. He could pull through, or he could get worse.
"All one can say is that the bleeding, we think, is easing – but he is very seriously ill on a ventilator.
"His condition is stable but he does have a particularly nasty complication with bleeding from his bowel. It is a complication that we don't fully understand, we don't know why this is happening and have changed all of his antibiotics to try to get on top of it. I have looked after him for a long time and we are not giving up."