He had just arrived in the Alaskan city two days after climbing Denali (formerly Mt McKinley) to complete the seven summits - the highest peaks of the seven continents.
It was third time lucky for the 57-year-old - who climbed Mt Everest two years ago - after bad weather stymied his attempts in 2015 and last year.
''It's an incredibly hard mountain - by far the toughest I've climbed.''
Amazingly, Mr Dagg only began serious mountaineering after scaling Tanzania's Mt Kilimanjaro in 2011.
He has since climbed Mt Aconcagua (Argentina), Mt Elbrus (Russia), Mt Vinson (the Antarctic) and Mt Carstensz (Indonesia) as well as Everest.
But it was only after climbing the latter, in 2016, that he began thinking the seven summits was a realistic goal.
''I had no intention at all. I thought they'd be too dangerous, too tough, too steep.''
Despite experiencing gusty winds and temperatures between -25degC and -30degC on Monday, Mr Dagg says the trio were ''very, very lucky'' with the weather, getting a window of opportunity they seized upon.
''I was the weakest link, so as long as I could keep going, they could keep going.''
Theirs was the first commercial expedition to summit the mountain this year.
After being dropped on a glacier at an altitude of 2200m, the trio had to haul equipment and food for 21 days nearly 50km to an altitude of 4300m before beginning the climb itself.
''It's a tough, tough job, and mentally as well because of the weather - you'd have a good day and then three s... ones where you'd just have to sit in your tent.
''You're very close to the Arctic Circle and the Bering Sea, so you can get weather from two directions.''
Mr Dagg will not be home for a couple of months; wife Dale will soon join him in the United States for a holiday that will include him climbing Mt Rainier, in Washington state.
''But I'm also planning to sink quite a lot of beer, sit by the pool and read books.''
