"That's the thing with mental barriers; once you crack them the world's your oyster," he said from San Francisco this afternoon.
"Yesterday I was feeling great, the conditions were outstanding for discus throwing and it all came together.
''I was a bit dumbfounded to be honest. Technically it was one of the best throws I've put together in my life.
"I'd had really good training sessions (with coach Matt Dallow in San Francisco). It was not like it was unexpected.
''I knew a good throw was in there; it was just a matter of getting it together on the day and getting it done."
Hall admitted after he rang his family he sat in his car for a while alone, getting his head around what he'd achieved.
Now there's a problem. There are no more meets in the United States where he can throw; the New Zealand season is over, so the search will begin in earnest when he returns home tomorrow for throwing opportunities.
Hall is ranked 20th for this year and it's understood the International Amateur Athletics Federation will want the top 32 - with a maximum of three per country - at the worlds.
That means they might issue invitations if there aren't enough confirmed qualifiers.
However the 28-year-old, who works for the Ministry for Vulnerable Children in Auckland, wants to nail the mark of 65.3m, which is the B standard for London, simply to confirm the trip, satisfy himself and to show he'd got there under his own steam, rather through an invitation.
"To be honest the world champs weren't even on the radar; my focus was on getting to the Commonwealth Games."
What a difference one spectacular athletic moment can make.
Hall's eight national titles came in nine years. The winner in that odd year, 2013? Olympic shot put silver medallist Tom Walsh.
"Ha, yes. He still reminds me about it," Hall laughed.
New Zealand's team for the world championships in London in August is: Tom Walsh (Christchurch, shot put), Jacko Gill (Auckland, shot put), Angie Petty (Canterbury, 800m), Camille Buscomb (Waikato/BOP 10,000m), Zane Robertson (Waikato/BOP, 10,000m), Eliza McCartney (Auckland, pole vault), Joseph Millar (Waikato/Bay of Plenty, 200m), Quentin Rew (Wellington, 50km)