Instead he stuck to his guiding management principle and told Keegan: "If you think it is right for the club, go ahead."
In football, as in business, Sir John believes in appointing the best man and giving him the power to get on with it. Thus, though he was surprised by Keegan's decision to sell Newcastle's leading scorer and cult hero to Manchester United, he backed him.
"My first thought was `What!?' " Sir John admitted this week. "But now I think it is a good deal." So do the Newcastle public, according to local media surveys.
Keegan, underlined Sir John, was looking at the club's long-term future. Since Sir John gave him a rare 10-year contract to do that (and keep him from England's clutches) he cannot complain. "Kevin is the strategist on the football side," Sir John added."He has got to dictate where that is going, how to approach each stage."
So far Keegan has built and dismantled two teams. One saved Newcastle from relegation to the lower divisions three seasons ago; the other brought them into the Premiership a year later. Now he is seeking to transform the side that led the Premiership in the autumn, but proved fragile in the winter and Europe, into a team that can cope with both.
"If you are going to be anybody you have got to win the Premier League and get in the Champions' Cup," Sir John said. "The Cup-Winners' Cup, the Uefa Cup, they are secondary features.
"That is our ambition at Newcastle. We will do that in the next five years - there is no argument. But some people want it overnight - having come from where we have come from, that is not on. We still have massive debts. We have increased turnover from £5m to £25m in two years but it will be another two before we are profitable.
"By the end of the season we will have spent £22m on the ground, £22m on players and we inherited a debt of £6.5m." He added, with a wry smile: "They just roll off the tongue - but they are big figures. A lot of cash."
Sir John mentions money a lot, but that is his responsibility. He admits it was a big shock coming from business to football and discovering how clubs were run - "like holiday camps". His family is also personally involved to the tune of £14m - "pump-priming money," he says. It is a lot considering he never wanted to become involved and, when reluctantly persuaded to, merely put in half a million to "act as a catalyst".
It was Bob Cass, a North-east based national sports journalist, who finally talked Sir John into investing. The commitment was made over a bottle of whisky in a Portakabin by a building site. The site was by the MetroCentre, the shopping city that had cemented Hall's fortune and made his name. It led, probably uniquely, to his earning the admiration of both Baroness Thatcher and the Geordie masses.
"I never really wanted to own a football club but I got a name as someone who was doing something for the area - that is why I got my knighthood," Sir John said. "My name became synonymous with success and I was identified as someone who might do something for Newcastle."
This is all said without a trace of arrogance, or self-importance. The 61-year-old's dominant attitude is enthusiasm. He is an ideas man, ambitious and determined. One of those people who rocks back and forward in his chair while talking, his arms and hands gesturing like Magnus Pyke.
It is not hard to see why he has been so successful in business and football, nor how he can irritate the more cautious thinkers of the Football Association. He would be a difficult opponent, as the old Newcastle board found when they were ousted after abitter boardroom battle in late 1992.
By then Keegan was aboard, head-hunted not by Hall but by a group of directors including his son, Douglas. They convinced Keegan to join the club, then persuaded Sir John to appoint him.
"I did not know Kevin personally and I said `he's been out for the game for eight years'," Sir John said. "But they told me he was the only one who knew Newcastle and what it meant to the fans. I met him for 10 minutes and I was convinced."
Sir John remembered this week, as Cole headed for Manchester, that he had also needed convincing about Keegan's decision to buy Cole two years ago.
The relationship between a chairman and his manager is the most important element in the success of a football club. In Hall and Keegan Newcastle have a potent combination.
The similar background helps. Both their fathers were miners in the North-east's once productive coalfields. While Keegan's footballing talents kept him above ground, Hall followed tradition, going down the pit at 16. He worked as a mining surveyor for 12 years before qualifying as a chartered surveyor.
He left, went into property development and made his fortune - an estimated £40-50m. His company, Cameron Hall (his wife, Mae, was born a Cameron), is now run by Douglas, Sir John concentrates on Newcastle United.
"I began watching them at the age of eight," Sir John said. "My father, who was a fanatic, took me. We stood on what was then a dirt terrace and I would be at the front having been passed over the heads of the fans."
Echoes of a different world. But he is not nostalgic - of the change to all-seat stadiums, Sir John said: "In the next generation kids will say: "Daddy, did you actually stand at a football match? You stood in the rain? What was it like? You must have been very poor?"
In the Fifties they watched Newcastle lift the FA Cup three times in five seasons at Wembley. In time Douglas, too, took his place among the menfolk but, the 1969 European Fairs' Cup win apart, there were no more successes, just years of under-achievement.
Now "The Toon" are back and carrying the hopes of a region which has lost its industrial heart. "We are like the Basques," Sir John said. "We are fighting for a nation, the Geordie nation. Football means so much to us, it is part of our lives. Football is tribalism and we are the Mohicans."
Sometimes the passions involved even frighten the club. It is not just the man with the two-day-old tattoo of Andy Cole on his thigh or the new father who has christened his boy Cole that have been upset by the transfer. One man held up his three-year-old son and claimed he was distraught, another said his seven-year-old boy was suicidal.
It is a heavy responsibility and, after a homesick Cole briefly walked out last season, the club acted to ease the burden. A personnel department has been created which, for example, helps new players choose housing and schooling for their children.
"They have to understand they are coming to a region where football is a passion," Sir John said. "They have to take the adulation. The rapport with fans is tremendous, everybody plays their part - going round schools, signing autographs. We take out money from the community and they understand we have to put something back."
The amount of money taken out is a matter of controversy, with some supporters claiming they are being frozen out by high prices - notably the £500 "bond" which guarantees a season-ticket for 10 years. It is an argument that leaves Sir John unmoved.
"They have to decide what they want. Do they want to go back to the days when they could get in and not have any success. Or do they want to win the Premier League and get into the Champions' Cup? There is a price to pay if you are a big club. You have to build a stadium, a squad, put money into youth development."
Newcastle are trying to create in five years the same structure that Liverpool and Manchester United have built over decades. Having got within reach they are now looking to match the likes of Barcelona and Sporting Lisbon.
"When I took over I toured the top clubs in England, looked at their stadiums and turnover," Sir John said. "Last summer I visited the big clubs in Spain and Portugal. I want to create a sporting club here like the ones on the Continent."
There are plans to put another deck on the Milburn Stand, to build a scenic elevator and a rooftop restaurant. The ground, which already looms over the city centre, will, Sir John said, "be a beacon all over the city". There are also plans to create a football academy, a health club, a centre for sports medicine and to diversify into other sports. Sir John envisages the Brendon Fosters and Steve Crams of tomorrow running under the "Sporting Club of Newcastle" banner.
"The talent is here in the North-east," Sir John said. "If they give us planning permission for the academy I will give a promise that no Geordie kids, no Alan Shearers, will leave this area if they want to play for Newcastle. We are giving notice to theother clubs - no more will you steal our players."
The Academy is planned in a green-belt area, but woe betide any local councillor who defies such a clarion call - and pity cash-strapped, calcified Sunderland, too, as they struggle to compete.
"They must get their act together," Sir John said in an echo of his views on all such clubs. "Swan-Hunter went to the wall, why should a fooball club be different. People need time to get their act together, but if they don't why should fans of Newcastle, Manchester United, etc, subsidise those clubs who are not prepared to help themselves. We have to level up, not level down.
"There is a responsibility to help clubs initially, but not in the long term. If there is nobody in Gillingham with pride in his area, who is prepared to get hold of the club then they have to go part-time and find their place in the hierarchy of football. If Gillingham go out someone else will come in. It is a market-place."
Thatcherism to the core. It is a harsh message from one of the men steadily gaining power and influence in the game. But, as if remembering his motto, "capitalism with a social conscience", he tempers it.
"The days when the lower clubs had the same rights as the top clubs have gone for good, they have to realise where the power lies. But the chairmen of the Premier League have to accept responsibility for the overall game. If we have to take something offthe top of the TV deals for the good of the game, we should, and there are a lot of forward-thinking chairmen who feel the same way."Reuse content