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 council will look at proposals to build a new English-medium school to replace those in Gwernyfed and Brecon.
It also recommended a new school be built in Builth Wells, replacing the town's existing high school and the one in Llandrindod Wells.
If approved, it is hoped the plans will cut costs and tackle the issue of surplus places.

A freedom of information request by Plaid Cymru revealed the Labour-run authority had paid out £144,000 for the legal costs of nursery campaigners.
It also paid the £97,500 legal bill of successful library campaigners.
The council said costs in such circumstances usually fell on the authority which was "regrettable".
RCT had previously revealed that its own external legal costs came to £113,199.
Parents took their fight to the High Court in May to overturn the council's decision to end full-time nursery education for younger children.
Meanwhile, in the same month, campaigners chained themselves to bookshelves to protest against the proposed closure of Rhydfelin library.
They were granted a judicial review before it was reprieved.
Plaid Cymru said the money would have been better spent on frontline services.
It said the council had tried to "railroad" local people and it had been "a very expensive mistake to make".
A council spokesman said due to continued UK government cuts unpopular decisions had to be made.
"As is their right, residents can and have challenged these particular council decisions which, in respect of the decision to make changes to the funding arrangements for nursery education, resulted in the council's decision being quashed."
The former Goldman Sachs banker Jim O'Neill is passionate about a lot of things - Man Utd being one of them.
[NEXT_CONCEPT]
Plans to overhaul secondary schools in Powys will be discussed next month.
[NEXT_CONCEPT]
Rhondda Cynon Taf Council (RCT) has had to pay a £350,000 legal bill over challenges to cuts in nursery education and Rhydyfelin library's closure.