Kelly, 71, made 512 appearances for North End, a Deepdale record, and in 2001 the Alan Kelly Town End was named after one of Preston North End's greatest ever goalkeepers.

Kelly's son, Alan junior, said: "Dad had an emergency operation for colon cancer, and, thankfully, that has saved his life.

"Unfortunately, he had a very nasty infection after the operation and has been quite ill since. He has been in hospital for seven weeks, but he is on the road to recovery now.

"The surgeon says it is a positive outlook, but obviously it has come as a tremendous shock to dad, and he will have to undergo a course of chemotherapy and radiotherapy as part of the treatment.

"Dad, I think, always thought he was invincible."

Leave your messages of support for Preston North End legend Alan Kelly.

Alan junior and his brother David, who also lives in Preston, flew out to Washington DC, where their father has lived for the past 20 years, after learning of the seriousness of his illness.

"Dad doesn't like a fuss so he was a bit shocked to see us when we walked onto the hospital ward," added Kelly junior, who also started his league career at Deepdale.

"He just said to us, 'There is life in the old dog yet lads', and it was great to seeing him smiling."

Kelly was forced to retire in September 1973 following a shoulder injury against Bristol City, but later went on to coach North End, first as assistant manager, and then as first-team boss.

He resigned in 1985 and moved to America shortly after to run a goalkeeping school in Washington.

He made 447 league appearances for PNE, but it was his remarkable consistency that made him one of Deepdale's best loved keepers.

In five successive seasons from 1966, he missed just five games out of a possible 214 league fixtures and was never dropped.

He is the Republic of Ireland's most capped goalkeeper after Paddy Bonner, winning 47 caps for his country.

He made his international debut at Wembley in 1957, England winning 5-1.

Signed by manager Cliff Britton from Irish club Drumcondra in 1958, Kelly made his Preston debut in an FA Cup fourth-round tie at Swansea, after Fred Else had fallen ill. George Ross, who played in Preston's 1964 FA Cup final defeat to West Ham United at Wembley alongside Kelly, said: "I'm sure every Preston fan will hope and pray Alan pulls through.

"He is a fantastic guy and a true North End great.

"I spoke to him on Tuesday and the first thing he asked me was how the family was.

"That's Alan Kelly for you, always kind, thoughtful and considerate.

We've remained great friends over the years, as we were at Deepdale when we played together."