He is also a firm believer in the Northern Powerhouse and close relations with China.
Both have found themselves under scrutiny since Theresa May became Prime Minister.
Lord O'Neill was very much a George Osborne hire. The former chancellor was delighted when he agreed to join the Treasury team.
His departure sees the dismantling of another part of the Cameron-Osborne legacy.
I doubt Lord O'Neill felt all that comfortable in a May led administration, evidenced by his decision to quit the Conservative whip in the Lords and become a cross bencher.
And the Prime Minister has been clear - this is a new chapter in Conservative politics and Lord O'Neill, as anyone who has met him will attest, is not a natural Tory.
The fit just wasn't comfortable - particularly when it came to non-Treasury issues like the re-introduction of grammar schools, a policy that Lord O'Neill does not back.
Turning to the resignation, I am told that Lord O'Neill was particularly perturbed about the handling of the China issue.
At Goldman Sachs, he coined the term BRICS (standing for Brazil, Russia, India, China) to focus minds on where he believed the main drivers of growth would come from in the 21st century.
His 30 years in banking certainly made him an expert on China which he travelled to regularly.
It wasn't that he was necessarily a supporter of the Hinkley C project.
He just felt the way it was handled damaged relationships with this most sensitive of countries.
There were reports before the summer that Lord O'Neill was considering his position.
But it appears that after a meeting with Nick Timothy, Theresa May's chief of staff, he was reassured enough to remain until at least the completion of the Antimicrobial Resistance Review he was initially brought in to complete for the government.
With that issue - and Lord O'Neill's reports - now in the hands of the United Nations, this was a more comfortable departure point.
And the government, as Lord O'Neill says in his resignation letter, has at least made some commitments to the continuation of the "golden relationship" with China and to the promotion of economic regeneration in the north of England, whatever it might ultimately be called.
For Lord O'Neill, there will be plenty of organisations on the phone, looking for a little of his expertise.
He might even receive a call from Mr Osborne, who has launched a business-funded think tank to support economic regeneration in the north of England.
The former Goldman Sachs banker Jim O'Neill is passionate about a lot of things - Man Utd being one of them.