He seemed to take some paternal pride in Bridges' assent, talking about how he had watched as Bridges had "grown" from backbencher to minister to leader.
Asked if he considered himself Key's son from another mother, Bridges laughed and he said he was more like Key than Bill English "in a personality sense".
"We both share a bit of jokiness and blokiness."
Earlier in the day he rather immodestly compared himself to Key on RNZ's Morning Report: "I think he had something that I have, something I hope I have, which is a lightness, a humour, but also a seriousness of purpose."
Down the hallway, Bridges' new office has Leader of the Opposition on the door and is full of boxes, wrapped up pictures and replica planes that are gift of choice for Transport Ministers.
The office was recently vacated by English.
Bridges looks through the cupboards for any evidence of English's occupation but all he finds is a shoe buffer and empty coat hangers.
There is no bottle of wine or even a note left by way of a "good luck'"to his successor and English will no doubt be back to reclaim the shoe buffer once he reads this.
English has even taken the nice leather chair, leaving Bridges with a tiny battered swivel chair.
"He wasn't one of the world's best finance ministers for nothing," Bridges observes.
A long string of people had started in this office with just as much vim and self-belief as Bridges.
It may need its feng shui addressed, for the vast majority did not fare well.
Between 1999 and 2008, National churned through Dame Jenny Shipley, Bill English, and Don Brash before Key's lucky cufflinks broke the bad juju and got them into Government.
Between 2008 and 2017, Labour went through Phil Goff, David Shearer, David Cunliffe and Andrew Little before Ardern managed it.
History is not on Bridges' side and although he studied history he also believes he can defy it.
He has run marathons but is not good at sports: "co-ordination levels are not particularly high".
That might explain why the leadership of Simon Bridges began with an own goal, although Bridges insists it wasn't.
That was when he tried to puncture the hoopla around NZ First MP Shane Jones' "Provincial Growth Fund" by revealing a $350,000 grant was going to a company in which one of the directors was being investigated for alleged conflicts of interest during the Christchurch Earthquake rebuild.
It was quite the hit.
Alas, Prime Minister Jacinda Ardern quickly discovered the National Government itself had given about $50,000 to the same company.
Bridges insists that pre-dated the investigation and further funding was declined.
But explaining is losing, and Bridges knows it or will soon discover it.
Bridges has also already executed another rite of passage for a new leader: the U-turn. There was a partial U-turn on gay marriage, which Bridges opposed but says he is now happy with.
The other one was the infamous promise to upgrade 10 bridges in Northland during the Northland byelection.
Bridges now concedes less may have been more.
"In the heat of a by-election, not the smartest move."
He insists the four or so that are being done are much needed: "And you know this to be true!"
All these U-turns and concessions come on Bridges' first full day as leader of the National Party.
He begins the interview by announcing he is tired. It is 4pm, he's had a busy 24 hours and he is a morning person. "That's good, I'm hoping you'll be weak," I say.
He has spent the day running from room to room for media interviews.
But he's seen short honeymoons before for Leaders of the Opposition and does not plan to waste a second of his lest the post-nuptial bliss gets cut short.
So here is talking about how he met his wife Natalie and being a Young Nat.
Bridges met Natalie, who is British, when both were at Oxford University in 2004-05.
Bridges was doing law. Natalie was doing a Masters in Romantic Poetry.
They met by the cubby holes where the mail was put. "And she thought I was a good-looking Japanese guy."
"I was thinner and more muscular then.
"I took her on a date to a Singaporean noodles bar. It didn't end particularly well because on the way back we got takeaway coffees.
"It was very hot because I had it black and I spilled it all over my hand and burned it quite badly. But we kept on going out."
They married before Bridges returned to New Zealand at the end of that year.
The Reverend who married them at Oxford pulled Natalie aside and warned her against it.
"He wanted to warn her to make sure she knew what she was doing because he didn't want her to marry me. She was 22 and I was 28 and she was going to the other side of the world."
He points to photos of their three children, Emlyn (5), Harry (3) and Jemima (3 months) and boasts he proved that man of God wrong.
Bridges was working as a Crown prosecutor in Tauranga and thinking about moving back to Auckland when then National MP Bob Clarkson decided he didn't want to stand for Parliament again in 2008.
Bridges stood against NZ First leader Winston Peters, who was trying to reclaim the seat from National - and won.
He had been involved with the National Party since he was 16. He was a Young Nat, an organisation he recalls was populated by "a bunch of pimply young blokes".
His family – Baptist minister father, at-home mother and five siblings – were not political and politics was not part of their dinnertime conversation. "I was a self-starter."
Former Labour MP Chris Carter was his teacher at the time "and I liked him". But he decided his "values" were more aligned with National: "getting ahead on your own steam".
His only brush with Labour after that was in 2002 when he did an internship with UK Labour Party MP Austin Mitchell at the House of Commons. He still uses the mousepad he brought back with him.
It was not his childhood ambition to be Prime Minister. His ambition was to be the conductor of an orchestra. "I used to practice with chopsticks to the William Tell Overture."
In his teens he wanted to be a talkback host. He even applied to do a journalism course at the end of his sixth form year, but was rejected.
He lists his accent as his worst feature. He can also have a bit of a croak.
A "helpful constituent" once sent him a note about his gravelly voice and offered a technique to get rid of it before big speeches or interviews.
"It is effectively emulating the sound of a cuckoo. To the tune of Do-Re-Mi.
So if I croak, you'll know I haven't done it."
His eyes eyes flick to his press secretary, Michael Fox, when he is asked for a demonstration.
Fox, who was handed down from Key to English and now Bridges, gives Bridges the eyeball.
"John Key at his height might have done it, but I am not at my height," Bridges says.
John Key might have begat Simon Bridges, but Bridges has a few tricks to learn about the media and the capacity for revenge.
He laughed at length when this reporter tripped and fell on to a sofa. "That's God punishing you," he said.
So let it be known Bridges' hates being called "Si." Absolutely loathes it.
Now that we know this, everybody must take care not to call him Si.
