Coached by his father, Morpeth got the good news about the overall record later in the day.
"I knew I had the nationals record at prizegiving; then when everyone had left, the official came up and said congratulations [for NZ record].
"We pretty much train every night."
Like Renee Tears in the road events at Kowhai Park, Morpeth had taken full advantage of having the Rivercity tour races in November as preparation for the nationals, held in the same locations with predominantly the same opposition.
Hoping to win the overall aggregate for his age group across the three national events, Morpeth had a two-point lead by yesterday afternoon and was looking forward to the Cemetery Circuit racing tomorrow.
In addition, it was a good comeback to competition for 2014 world masters marathon silver medallist Krystine Davies, who set a new national record in the Masters Ladies 3000m, which included beating the previous record holder in South Canterbury's Leah Caldwell.
Not surprisingly, Jones went out and set a new fastest time for the Senior men's 1500m, while Smith said that Begg continues to "clean up" the Senior women's.
However, Whanganui's Melissa White also performed well in the division, coming second to Begg in the 3000m and third in the 1500m behind Begg and Valley Inline's Georgia Hurley.
Whanganui's Andrew Jones was also second in the Senior men's 300m time trials on Thursday.
Josh Valentine won the Primary boys 400m final, where teammate Lucas Hodgson was third, competing at his first New Zealand championships.
Stefan Tears continues to have a competitive rivalry with Timaru's Nick Farmer in the Intermediate men's grade, finishing second to him in the 1500m for another 1-2 finish.
"Though Nick's a little bit faster, Stefan's closing in with every race," said Smith.
The indoor events will conclude today with more relay finals, with the Cemetery Circuit on Sunday.