Charles features highly in polls of the greatest Welsh sportsmen

Sports journalist Bob Harris said the former Leeds, Juventus and Wales forward does not enjoy speaking about himself or his achievements.

But after months of research and endless hours in Charles's company the book - King John - is now bound for the bookshops.

"The man is so inherently modest - he was very difficult to do a book with because he simply does not like to talk about his great feats and achievements," he said.

He keeps such a cheerful demeanour and he is such a happy and pleasant man Bob Harris

Charles regularly features highly in polls of the greatest Welsh sportsman and is still revered in Italy where he is affectionately known as Il Buono Gigante (The Gentle Giant) because he was never booked or sent off.

"He was without doubt one of the five top players ever," said Mr Harris.

"Had he lived in a different era John Charles would have been talked of around the world, not just in Wales, in the same breathe as the likes of Pele and Maradona.

"But he did not make big money at all.

"They got decent bonuses when he was at Juventus but the wages were side by side with British wages which were around �20 a week."

Charles now lives in Leeds with his wife Glenda and will be the subject of an exhibition that will kick-off in his home city of Swansea next year before touring the country.

there were small children running up to him and grizzled old veterans and to them he is still the king. Bob Harris

The footballer has been diagnosed with Alzheimer's disease which means his memory is not what it was.

"Fortunately he retains a lot of his memories of older days but it is quite difficult for him and for someone who is doing his book," added Mr Harris.

"But he keeps such a cheerful demeanour and he is such a happy and pleasant man that it was never a problem."

As part of the research the two men visited some of Charles's old stomping grounds in Italy.

Mr Harris said: "He played for Juventus for five years and had a brief spell with Roma.

"We took him over to a place just by the old training camp and there were small children running up to him and grizzled old veterans and to them he is still the king.