After recovering and re-fitting an old coastal steamship in Auckland's shipyards, the team travelled north to Whangarei Harbour where they commissioned a special diving chamber, "the Bell", to be made locally.
Human diving capabilities had barely reached 121m depth by the 1940s but an Italian team had succeeded in reaching a shipwreck at a similar depth. Their diving chamber was copied to make "the Bell". The crushed handle of a silver dinner knife recovered from the wreck displays the effects of the intense water pressure at this depth.
Local man John Thomson recalled living next door to the diver's accommodation at the time, and as a 14-year-old Whangarei Boys' High School student obviously did enough pestering and showed the right type of pluck to be invited on to the Claymore for a fortnight and experience the salvage first hand.
The outing did not disappoint. Mr Thomson came back with stories of knife throwing, vomiting out of windows, and nearly going down in the Bell with diver John Johnstone, except that they'd found a small leak that had to be repaired. Mr Thomson, now in his 80s, said he didn't mind missing this last bit.
He described the hardest part being the months of toil just to locate the Niagara wreck as it had drifted north.
After many false alarms, when great rocks were hooked, the crew finally sighted the Niagara's port holes.
On each visit the Claymore lined up with kauri log floats directly over the wreck and anchored to six tonne concrete blocks. A winch and a "grab" were guided from the stern with directions conveyed up a phone line attached to Mr Johnstone deep in the water inside the Bell.
In this way they removed debris stage by stage and positioned explosives to blast through the Niagara's three decks and the Bullion Room door to reach the gold. After 316 dives and several close escapes with floating mines, this team collectively recovered 555 gold ingots and a handful of artefacts.
Mr Thomson recalled, "Diver Johnstone told me and several others that he was coming up in the Bell with the drag going up and a bar slips through the teeth and he reached out to grab it and barked all his knuckles on the inside of his bell.
"We asked him what happened to your knuckles and he said yeah, it disappeared down into the mud, oh he said it was frustrating. But they had a lot of gold on board that time."
The gold was collected straight off the wharf by a representative of the Bank of England.
Mr Thomson described, "And oh you know it's heavy, you could only carry two ingots at a time. There was a couple of guys standing there with .303 rifles, which is a bit old fashioned for these days but in those days it was quite significant".
All of this activity at the wharf boosted Whangarei's engineering industry, particularly through ongoing maintenance of both the diving Bell and the Claymore.
Not satisfied, John Johnstone returned with a new, smaller diving bell in 1953 and recovered a further 30 gold ingots.
This final journey seemed to satisfy both the public and the Bank of England and the wreck was left for nearly 50 years due to the difficulty of access at that depth.
More recently Keith Gordon has purchased the salvage rights to the wreck. His book Deep Water Gold is available in the Kiwi North gift shop.
Developments in underwater robotic vehicles (ROVs) and diving breathing equipment have allowed Mr Gordon to further explore the Niagara and it is now a popular deep water diving spot.
The five remaining gold bars, worth around NZ$1.4 million in 2006, remain lost to this day.
Thank you to John Thompson for sharing his memories and Keith Gordon and the Reynolds family for artefacts on loan at Kiwi North.
■ Georgia Kerby is exhibitions curator, Whangarei Museum at Kiwi North
