Their biggest challenge came against Keith Cocking and Merv Tane, the No2 seeds, in a all-Northland affair.
Clapshaw and Mitchell picked up the first set 6-2 before clinching the title with a 6-3 win in the second set.
In the Women's Doubles A division, seedings again proved right with Paul Jane Stubbing (Mission Bay) and Shelley Yeates (Springfield) winning the title after a three set thriller.
Stubbing and Yeates eased through their first two matches, accounting for the pairings of Frances Coutts and Alyce Kelly (6-3 6-1) and fourth seeds Raewyn Heywood and Judy Hill (6-3 6-2) in straight sets.
This set up a date with third seeds Leona Davis and Aliya Edwards to decide the title.
Stubbing and Yeates got off to a flier, winning the first set 6-1 and looking likely to win at a canter.
However, Davis and Edwards fought back to win the second set 7-5, leaving it to a tie breaker.
The class of Stubbing and Yeates came through in the decider, taking it out 10-3 to win the title.
All four competitions were won by the No1 seeds.
In the Men's Doubles B division, Springfield's Chris and Greg Miller were pushed to the brink on route to the title.
Their semifinal against Hayden Craven and Willie Rankin went to a tie breaker, which the Millers won 11-9.
It was an identical story in the final against No2 seeds Will Ian Flavell and Jordan Winiata, with the match again going to a tie breaker and the Millers again coming out 11-9 winners.
Craigie and Elma McCullough took out the Women's Doubles B division after ousting the No2 seeds Sacha Pou-Tito and Ivy Rakich in a tie breaker.
The McCulloughs won the first set 6-4 before Pou-Tito and Rakich clinched the second set 6-4.
In the end it was the McCullough pairing who held their nerve to win the tie breaker 10-3.