"I ran my first marathon as part of the race in 3 hours, 12 minutes," Mr Thompson said.
"Then took public transport back to near the start line in Greenwich before running the second marathon in 4.24."
He said mental strength and visualisation got him across the line.
"I'd like to say hard training and a strict diet, but I'd be lying.
"I felt pretty rough after the first lap due to heat and lack of preparation, and Dad was suggesting I was best to call it quits and that I wouldn't be letting anyone down.
"I pushed on and when the folks next saw me, at about the 60km mark, I had perked up and was feeling much better."
He said he was a "tad embarrassed" to be nominated for the award.
"This whole experience was never about me. If this nomination brings further awareness to the ongoing support that the Starship Foundation needs, then that can only be a wonderful thing."
A total of $13,210 was raised by Mr Thompson. The Pride of New Zealand Awards are sponsored by The New Zealand Herald, The Hits and TSB Bank.
For more information and to nominate, visit prideofnzawards.co.nz.