Up until about four years ago he had been living in Auckland with wife Vanessa and their two teenage daughters, having arrived there with his parents from the UK when he was two.
It was time for a lifestyle change, he said, adding that they looked at two potential spots — Tauranga and Napier.
His wife had been born in Hawke's Bay so Napier got the nod.
So did the pursuit of a place in the automotive industry.
"I always liked cars."
He knew the manager of City Collision Repairs, Chris Greaney, because his sister-in-law had been involved with the company's website.
So he started making a few calls to Greaney about the possibility of joining the 12-strong crew there.
"And I went round there a couple of times and kept at him," he said with a smile.
"I twisted his arm."
Greaney said he had initially been reluctant to take him on as an apprentice - usually the domain of the late teens like two new ones he is set to take on - due to his age.
"But he kept at me."
So he arranged for "Marty" to apply for one of the limited places in the IAG Trades Scholarship scheme, and both were delighted to get the call to say he had been accepted.
"They paid for my training and even gave me a toolbox," he said.
So, as he looked forward to his 48th birthday, the three-year apprenticeship started and as it can be for the "young fellas" on the floor he got to do a bit of sweeping up and make the tea from time to time.
On the panelbeating front he simply excelled.
"He was totally committed to it and became a very loyal employee," Greaney said.
And his younger workmates soon got used to the new boy being as old as their fathers, and Thornicroft and the family love it here.
"Lifestyle, the climate, love the job — everything."
Greaney agreed with his newly qualified employee that age is but a number.
"If they are physically able, anyone of any age can take something on."
Thornicroft's advice to those of more mature years contemplating a career change?
"Give it a go."