It is an unlikely scene.

A former deputy governor of the Bank of England scribbles figures on the back of an envelope. The numbers are crunched. The bottom line is reached. Brian Quinn has travelled more than 500,000 miles in his seven years as chairman of Celtic. It was a calculation made this week as he anticipated his departure from the club's board.

"I miss only about four or five matches a year," he said. "I reckon I have travelled half a million miles between matches, board meetings, supporters' functions, UEFA meetings, overseas matches, tours and so on."

Quinn, who will be 71 in November, added yesterday: "There comes a time when somebody else had to do it."

There are other figures. Celtic won five SPL titles, four Scottish Cups and three League Cups under his careful stewardship. The chairman watched 315 league and cup matches and made 90 trips abroad on European business, whether for matches or UEFA conferences. He also chipped in £5000 to the fund for the Brother Walfrid statue, though this is a figure revealed quietly by a Parkhead source.

Quinn, diffident and sober, will be embarrassed that this donation has reached the public realm and that his last board meeting was on the splendour of the QE2 as it was anchored off Greenock.

He has, after all, earned his considerable reputation not on the back of envelopes or flamboyant gestures. He is a major financial player. His achievements are measured on balance sheets. It on this dry, but crucial playing field that his contribution to Celtic will be measured.

"At a certain point about three years ago, I decided with Dermot Desmond that it could not go on," said Quinn. "You shouldn't run a company like this."

He was referring to a financial position that was untenable at the club. "We ran up cumulative deficits over the years of in excess of £40m and we were funding those deficits ultimately by shareholders' contributions through rights issues. Although we were achieving a certain success by then on the football field under Martin O'Neill, you can't go on losing money at the rate of £5m-£7m a year indefinitely."

This is said with the quiet but unmistakable indignation of a money man. It is followed by more business language: "We sat down to develop a new business model which we called the model of sustainability. We aimed to break even or do slightly better. Any rights issue should be for investment only."

Central to this strategy was to cut costs. Quinn praises Peter Lawwell, his chief executive, for his role in executing the programme. "We have changed our cost base and we have a way of paying players that is not based upon a large basic salary plus bonuses and much more on a small basic salary but big bonuses. So that if the players earn, they get. That has changed incentives inside the company and it has changed the performance of the club."

The other important factor was to increase revenue through sponsorship deals with the likes of Carling, Nike, MBNA and T-Mobile. "This has given us the comfort of a predictable income," said Quinn who has spent 11 years on the Celtic board.

He is cagey, too, about the significance of Celtic's recent £15m pre-tax profit. "It was extremely welcome," he said. "But there were a couple of factors you cannot rely upon for repetition. One of them was going into the last 16 of the Champions League and the other was activities in the transfer market. You cannot budget on those things."

But how does Quinn feel as a fan when he has to turn away from buying at the top end of the market? Did he ever feel a tension between what he wanted and what he could afford? "No, I didn't," he replied immediately.

"As the chairman of a public limited company you are absolutely clear where your priority lies. You have to do the right thing. And I never wavered from that."

This stance was not popular among fans who wanted Celtic to buy big. "Not many years ago we were being heavily criticised by supporters and I was regarded as Mr Prudent and got of lot of abuse. But I knew it was the right thing to do. I hope that doesn't sound arrogant," added Quinn.

He is similarly adamant on bringing in players, preferring to invest in the infrastructure of the club instead of huge transfer fees for which he has an institutional distaste. "We've seen where that road takes you," he said with palpable disgust.

Quinn met with resistance with fans on this strategy but also had a celebrated spat with O'Neill, the then Celtic manager, over the size of the wage bill. "If you are in a position of authority in any company and you never have a fight, then somebody is not doing his job," he said. "Martin was doing what he thought was best for the football team. I was having to say there are limits to this because we have to have a look at the financial implications of what we're doing.

The argument was over a particular piece of data.

"And I was right over that piece of data. There was a bit of a spat. It was an incident rather than a syndrome."

It shows the strong side of a man who climbed the mountains of the financial world from the base camp of Govan. It also helps explain why Quinn is leaving.

"I believe that proper corporate governance is at the very core of our success here," he said. "A part of that is not getting too cosy with one another. It is having a board which can be relied upon to be objective and rational in how they do things. There is an ever-present danger in any plc that if people are in place for too long it gets cosy and you don't take the difficult decisions. It is time for someone else to take over. I've done my piece."

He will, of course, remain a fan. "My dad was a supporter, his father was a supporter.

My two sons are season ticket-holders who fly up and down from London for games. I have even managed to indoctrinate two of my three grandsons. I am still working on my third one who is a big Liverpool supporter."

And, as a fan, what is his best memory? "It was when I was in the bowels of the stand in Seville before the game UEFA Cup final in 2003 against Porto and I went upstairs to have a look at the ground. I stood in the middle of the VIP stand and I heard the Celtic supporters singing Fields of Athenry, You'll Never Walk Alone and all the anthems and there was a great big lump in my throat. That's my abiding memory of supporting Celtic."

Asked about the best player, he replied: "Henrik Larsson. In a class of his own."

Quinn will keep himself busy in his roles as a non-executive director of a mortgage insurance company, a non-executive director of the Qatar financial services authority, work for the World Bank and the International Monetary Fund, and his financial consulting business.

Oh, and convincing a grandson that Liverpool red is never an acceptable bottom line on a balance sheet or for a supporter.