"It's my first-ever national champs title so I am pretty stoked.
"I made one pretty big mistake up the top. I was pretty sure I was going down.
"I don't know how I rode out. I was pretty lucky and I knew from there I had to make up time.
"For the amount of training I've been able to do with a back issue and a lot of travelling, I still have my fitness so it is super-cool and great to be back on the top step," he said.
"To be able to wear the national jersey for my new team Trek World Racing will be sick."
Blenkinsop finished second with visiting Frenchman Bruni Luc the third fastest in 2:51.05 but Kawerau's Matt Walker claimed the national championship bronze medal with the international rider ineligible for New Zealand honours.
Two-time world champion Emmeline Ragot (France), ranked No2 in the world, was in a class of her own in the women's race with a superb 3:14.21 effort with England's Jess Stone second fastest.
But the prize went to Christchurch-based Laird, her first national downhill title, ironically after deciding to limit her riding to domestic competition after several years on the international circuit.
She clocked an outstanding 3:31.70 to be half a second faster than favoured Alanna Columb (Queenstown) with Stophie Tyas (Christchurch) third in 3:32.29.
"I can't believe it. I had just about the perfect run. I could have pushed more but I knew I had to hold it together in the dusty stuff," Laird said.
"I don't ride so much now and I think it did help because you don't scare yourself with expectations and you come in feeling good and relaxed.
"For all these years I have been trying so hard to win and this year I was happy to cruise and have fun with my friends and it shows that when you are having fun it works out well," she said.
In other racing, Lawrence Cawte (Rotorua) won the under-19 honours in an outstanding 3:01.91 while Jack Humphries (Palmerston North) grabbed the under-17 title in 3:09.17.
Robbie Wong-Toi (Rotorua) won the under-15 title and Kieran Thompson (Christchurch) was the senior men's winner.
Phoebe Coers (Wanaka) won the under-19 women's title while Kaytee Campbell (Hamilton) claimed the open women.