The victory was achieved on home roads, securing the New Zealand Rally Championship and a record fifth national title for Richard, and it fulfilled a dying wish.
The Masons' long-term supporter and sponsor, Greg Horne, who died earlier this year, wanted the duo to achieve a fifth championship.
''This championship is for you, Greg Horne,'' the Masons said on social media.
''You wanted to stay around to see this but that wasn't to be. I know you'll be looking down and smiling.''
They produced a superb driving display and were fastest in all nine stages in their Subaru Impreza, winning the 163km event by 2min 44sec from second-placed Ben Hunt, of Nelson.
Richard Mason was ecstatic with the result.
''To wrap up the title at home after such a dominant year really is the icing on the cake,'' he said.
Third went to Tauranga Mitsubishi Evo 8 driver David Holder, his third consecutive podium result in the NZRC.
It was a tough event for several crews.
Te Aroha's Lance Williams, who was second in the championship heading into this event, crashed in special stage one.
Dunedin's Emma Gilmour rolled out of contention on special stage two in her Suzuki Swift Maxi. She and co-driver Ben Atkinson were unhurt but, although Gilmour's car was only superficially damaged, it was unable to continue.
''It was a slow speed roll, the Suzuki just stepped out on braking and as I was quite sideways into a bank, it used it like a ramp and launched up and over,'' Gilmour said.
The NZRC now breaks for two months before resuming at round five, the Rally of Coromandel.
New Zealand's Hayden Paddon and co-driver John Kennard improved their overall placing from 11th to seventh after three days of WRC Rally Poland.
Competing in his second WRC event with the Hyundai Shell World Rally Team, Paddon's 10 stages on the third day were largely trouble-free. He ran third on the road and continued to assess and tweak his driving to make noticeable improvements in pace.
''We learnt where we were losing time and maybe have been overdriving the car a little bit, so this afternoon it's all been about slow entry and trying to get a fast exit and the times have improved,'' Paddon said.
He struggled with the rutted stages, but learning to drive in rough conditions was part of his objective for these rallies, he said.
''From that perspective, it's been a good learning exercise. We're up to seventh, which is a bit of a bonus, and now we've got a bigger task tomorrow to try and hold on to that.''
A final four stages will wrap up the action today (NZ time).
