From the training farm he was transferred to the Masterton office as a stock clerk and did his OE, driving a combine harvester in the Cotswolds.
"The then master of the Masterton office, Eddie Watts, had a heart attack and I was summoned back to Masterton."
He said he could not afford to return so the company arranged a job on a ship bringing the first shipment of Charolais cattle to New Zealand and some pigs.
His job was shovelling "S H one T" over the side and arrived back in New Zealand on Christmas Eve 1969.
He became a stock agent in Pongaroa and married Ros, who hailed from Northern Ireland, and twins Richard and Caroline were born in Dannevirke Hospital.
"I was pushing cattle around the yards at the Akitio cattle fair and in came Harry Huse. I didn't expect to see him there - he was ex-chief general manager of the National Mortgage Agency.
"This was just after Wrightson and NMA merged to form Wrightson NMA."
Mr Stace was told with a wife from the British Isles perhaps he should go to London next.
"So from the sublime to the ridiculous I was transferred out of what I called the social and cultural centre of New Zealand - Pongaroa - to London to help run a business called the Genetics International Livestock Ltd.
"Genetics International was 50 per cent owned by Wrightson and 50 per cent owned by a man called Daniel B Thomas who had made a fortune from being Billy Graham's treasurer - the evangelist - and he had camped outside Ron Trotter's office in Wellington convincing him that exotic cattle were the way forward."
Mr Stace administered a programme of several exotic breeds at two farms which transplanted embryos.
The cattle were worth several million pounds and the programme had risks that needed insurance, but Mr Stace had little regard for the insurance brokers of the day.
"I thought the brokers were on the whole idle, so it would be easier for me to go and do the broking."
Lloyd's of London's were nearby so he popped in for a chat.
"In those days there was no security at Lloyd's and I just went in. I had a suit and tie on - probably fitted the type."
He was pointed to the desks of the livestock underwriters, where he was quizzed at length on the programme and was given insurance, but it still had to go through a broker.
"I fell in love with this market Lloyd's."
He returned to head office as a senior executive in the Export Division of Wrightson NMA in Wellington.
"I didn't last. About three years later I resigned and set up an insurance broking business called Harlock Stace Andrewes.
In 1977 he was invited to sign up New Zealand Members of Lloyd's.
Also known as Names, Lloyd's used wealthy individuals to back policies with unlimited liability and their assets regularly audited to ensure liquidity.
Using his farming contacts he invited dozens to join.
"The farming community were asset heavy and income light."
He was the first to source New Zealand Members of Lloyd's, but soon a "shipping fleet" of UK agents arrived to sign up individuals.
Mr Stace felt an obligation to protect the interests of the 70 people he had signed so moved his family, now including Susie, to London in 1980.
"It was wrong that I was in New Zealand and these people were accepting unlimited liabilities in London, so I wanted to be adjacent to where those risks were being taken."
For five years from 1980 he was with Donner Underwriting Agencies, a Lloyd's Members' agency, of which he was appointed a director in 1984.
With Alan Barr in 1985 he formed Stace Barr, which in 1997 was the largest manager/adviser of capital within the Lloyd's market, representing 9 per cent of Lloyd's 10.3 billion capacity in that year.
He was elected for the council of Lloyd's and served as deputy chairman of Lloyd's for 1995 and 1996, a time of "appalling grief".
Retrospective claims for liabilities emanating from things such as asbestos, pollution and breast implants meant large numbers of Members refused or were unable to pay losses.
Some alleged misrepresentation and negligence, including some in New Zealand, but Mr Stace said none were Members he looked after.
The market was forced to restructure.
He said at the peak of the market there were 33,000 Members of Lloyd's spread across about 307 syndicates with a market capacity of 14 billion.
"If Lloyd's had to cease underwriting, and it very nearly did, then all the 33,000 Members of Lloyd's estates would have been left open for the rest of their lives - they could not have been closed - because the regulator's priority was to make sure all claims could be paid. They could only do that if they had frozen the assets of all the Members of Lloyd's.
"It was absolutely critical that we found the solution and that's what the Reconstruction and Renewal programme achieved."
It proposed separating present Lloyd's business from past liabilities but many Names faced large debts.
He had the job of selling the plan to a hostile audience worldwide, including appearing on live broadcasts.
The reconstruction was adopted "by an overwhelming percentage" of the membership in late 1996.
He then went on to help broker a deal allowing corporate capital into the underwriting market - limited liability Names.
In 1997 he was CEO of Angerstein Underwriting Trust PLC and as a result of mergers and acquisitions it became Amlin PLC, which recently sold for 3.6 billion to Mitsui.
He got out in 2004, retiring as vice chairman of Amlin and the Lloyd's market so he could returned to New Zealand and his ageing parents after 25 years in the United Kingdom, settling in Havelock North.
He is by no means retired.
He is a director of New Zealand Thoroughbred Racing, a deputy chairman and shareholder of 3R Group, a director of Sportsground, trustee of The Tank Museum in the UK and consultant to the John Stace Geography Society at Westminster School in London.
With a house in the Marlborough Sounds he was the instigator of Sounds Air's decision to fly to Hawke's Bay from Blenheim this year, persuading the airline, business and viticulture communities a service was needed between the country's top wine producing areas.
The airport company thanked him for his "passion and enthusiasm in working to bring them here".
He keeps his eye open for opportunities.
"I love helping people that need advice and a leg up."
He has downsized his home, selling their mountaintop mansion in Havelock North, so more time can be spent overseas with their children and grandchildren.
"We thought the children might follow us out. The girls got married just before we came away and Richard married later and we thought they might come too. We now have four grandsons in England and one granddaughter in Dubai and want to see more of them, so that's part of our reasoning.
He doubts his career could be repeated in modern times, saying he was at the end of the generation where luckily being in the right place at the right time made all things possible.
"My life has been full of coincidences and opportunities, with a wonderfully supportive wife Ros."