Arguably the most eminent British businessman of his generation, he has taken the role of non-executive chairman to fine art, able to see the details of the deal as well as the broader picture.
Disciplined chief on top of the corporate world
In 2006, at the height of the delicate negotiations over the sale of the P&O ports group, Sir John Parker would sit in his London office overlooking Trafalgar Square and doodle.
These were no ordinary doodles. Sir Parker's drawings on a sheet of A4 illustrated the complex holding structure of Dubai World and the place within it of DP World, the Dubai group that was bidding - in rivalry with a Singaporean ports group - for ownership of P&O.
A lot was at stake in the merger talks. When - after some little local difficulty with the American authorities - P&O was eventually sold to Dubai for £3.9 billion (Dh21.9bn), it was a quantum leap for the emirate's ports group, then largely a regional operation based at Jebel Ali, to make it a global player in the top flight of international ports operators.
It was also the move that made DP World one of Dubai Inc's most valuable assets, and a consistent profit generator.
Sir John was the chairman of P&O and therefore had a duty to its shareholders to get the best price for the company. But he had left little doubt in talks with commentators and analysts that his preference was for a Dubai deal, rather than a Singapore one. Eventually, he pushed the deal through in Dubai's favour, but with a substantial premium for P&O shareholders, and left everybody happy - except, possibly, Singapore.
That deal was a prime example of the skills Sir John has made his hallmark at in a 40-year career at the top of the corporate ladder in the United Kingdom and globally.
It has been demonstrated in sectors ranging from shipbuilding, engineering and utilities to the global mining industry.
As probably the most eminent British businessman of his generation, Sir John has taken the role of non-executive chairman to a fine art. He is able to see the small details of the deal or corporate situation (hence the doodles above Trafalgar Square), but also the broader picture.
"I believe in discipline in the boardroom, but not to the point of ruthlessness. Leaders always in a tug of war between different interests, but the job is to keep channels open. Communication is the sister of leadership," he recently told an interviewer.
Last week in London, Sir John's skills at quiet diplomacy, backed by boardroom discipline, were on display again.
Perhaps the biggest and most time-consuming of the portfolio of senior non-executive jobs he has gathered together is the chairmanship of Anglo-American Corporation. Then in his late 60s, he joined the company in 2009, when others might have been looking for a quieter life. He made it obvious that he found the challenges exhilarating.
Back then, Anglo was facing a takeover threat from a rival mining company, and was riven by boardroom dissent, largely over the role of the chief executive Cynthia Carroll. It was a corporation in turmoil.
Sir John mended the boardroom divisions by making it clear he was standing firmly behind the chief executive, and made it obvious Anglo would not continue to be a sitting duck as a corporate takeover target.
The fruits of this work were on display at Anglo's recent results presentation. A new chief executive (Ms Carroll had eventually made a dignified exit in 2012) was being presented in the form of Mark Cutifani,who had a new strategy for Anglo. He also has Sir John's full backing, which will be important as the mining company adapts to a changing global environment for commodities.
After the Dubai takeover in 2006, Sir John was asked to stay on as the senior non-executive director of DP World, and insiders at the company pay tribute to the role he has played there. "DP World has had an eventful corporate life, and I'm sure they've been glad to have had Sir John's expertise to lean on along the way," said one.
He always has been an advocate of strong corporate governance, and was responsible for the governance structure within DP World, which regularly wins praise as one of the best-run companies in the UAE.
He was an enthusiast for the public listings of DP World shares (traded on Nasdaq Dubai and the London Stock Exchange) because of the strong governance regimes it would bring to the company.
Discipline, again, is his strong point. He learnt it first as the son of a farmer in Northern Ireland, and later at university, where he studied naval architecture and engineering.
An evening with Sir John can very often stray into discussion of the reasons why the Titanic sank, rather than the intricacies of the business world.
He had to maintain his own personal discipline in trying times during his stint at Harland & Wolf, the troubled Belfast shipmaker that became a political plaything in the 1980s.
Aged 71, Sir John shows little sign of slowing his commitment to the companies still within his portfolio, nor of relaxing that hallmark discipline. DP World will be grateful for that.