Charles, 67, is in remission after receiving radiotherapy and chemotherapy for the illness.

John Charles became a national hero in Italy

Known as the Gentle Giant during his playing days, he was equally adept as a striker or at centre-half.

A Leeds spokeswoman said: "Everybody at the club wishes him all the best. Anything we can do to help him we will."

Charles is rated by many as the greatest British footballer of his era, the finest Welsh player of all time and the most successful British soccer export.

Charles, a member of the only Welsh team ever to qualify for a World Cup finals, in 1958, was awarded the MBE in the Queen's Birthday Honours List in June.

John Charles still attends every Leeds home game

He said: "I have some good days, some not so good.

"But you have to keep going."

Charles, who still lives on the outskirts of Leeds, said in a recent interview: "There's not as much fun in the game today. It's all about money.

"Players these days are holding clubs to ransom and it's got to end or one or two clubs, and big ones at that, are going to go bankrupt.

"Players deserve to be well-paid but the system has gone out of all proportion. The money these days is unbelievable.

"When I played I earned £20 a week, though the bonuses were good in Italy. I once earned a £500 bonus at Juventus, which was big money in those days.

"But really we played just because we wanted to play. If you're grumbling about money all the time it's got to distract a player; it's got to affect his form."

Charity work

Charles, who was never sent off or booked during his career, still attends every Leeds home game and is an active member of the Leeds United ex-Players' Association.

Along with former Elland Road favourite Peter Lorimer, he tours the after-dinner speaking circuit raising money for charity.