Professor Roger Williams added that the suspected lung infection which prompted the hospitalisation last week was not directly linked to drinking by Best, who has battled alcoholism for decades.

The former Northern Ireland winger was in a "serious, but improving" condition at private Cromwell hospital, said Williams, who has cared for Best since he had a life-saving liver transplant in 2002.

Best had been "pretty miserable" when admitted to the hospital but was now "moderately cheerful", said Williams, adding that he hoped his patient would now stay off the drink.

"He can do it -- he did it before, get off the alcohol. He has had long spells when he does not drink," Williams told GMTV television.

Best, one of the most naturally gifted footballers of all time, began drinking heavily after he gave up playing, bringing a succession of health problems which led eventually to the liver transplant.

Williams said that Best was likely to remain in hospital for a week and most likely had a lung infection.

He had been made more susceptible to such illnesses because of the side-effects of medicines to suppress the immune system and prevent his body rejecting the new liver, the doctor added.

Best's agent Phil Hughes said Monday that the former player had been lapsing "in and out of consciousness" and was "very weak".

"The doctors say he's on the mend, but he still doesn't look good to me," he said.

Spotted as a 15-year-old, Best made his debut for Manchester United two years later and swiftly became a huge star, helping the club claim the English league championship in 1965 and 1967 and the European Cup in 1968.

Voted European Player of the Year in 1968, Best's ability, coupled with his good looks and sometimes wild temperament, led him into a party-going lifestyle which took an increasing toll on his career.

Aged just 26, Best walked out of Manchester United and top class football, despite another decade playing at smaller clubs in England, Scotland and the United States.

He then fully embraced a hard-living lifestyle, epitomised by a - perhaps apocryphal - tale recounted often by Best.

According to the story, in the early 1970s a bellboy brought breakfast to Best's hotel room to see the drunk ex-player in bed with the current Miss World, a magnum of champagne and a large sum of cash won from the previous night of gambling.

"George, where did it all go wrong?" the bellboy is supposed to have exclaimed.

In fact, Best's life became increasingly difficult as his health failed

and he had a number of brushes with the law, including convictions for drink-driving.

Less than a year after his liver transplant, Best was drinking again, prompting criticism from medical specialists that he risked putting people off organ donation.