He then spent three years compiling all he could about the only German submarine ever sent on a combat mission into the South Pacific.
And a submarine which had a shot at sinking the coaster Pukeko which had just set out from Napier Port - fortunately the torpedo its commander Heinrich Timm fired missed, and to this day is down there on the seabed near the port somewhere.
Mr Trevathan said he believed the story of Napier's brush with WW2 needed to be more widely told so he approached the Napier City Council and suggested it would be a good idea to put up some sort of storyboard detailing the submarine's voyage close to Napier.
Napier Mayor Bill Dalton and the council's Community Development crew agreed, calling Mr Trevathan's research and compilation of facts as a great project which needed to be shared with locals and visitors alike.
"It is a very interesting part of the history of our city," Mr Dalton said at yesterday's official unveiling of the storyboard which is set on the beachfront pathway near the Soundshell.
The citing was apt, Mr Trevathan said, as that was part of the lit-up seafront the crew would have seen.
"I'm really pleased this has happened because it's an important part of maritime history and Napier history, he said.
Equally pleased was Auckland author Andrew Harris who used the non-fictional arrival of the U-862 as part of his fictional tale of a German scientist managing to secretly make his way to New Zealand, and eventually settling in Havelock North, aboard it.
"I had to come up with a way to get this nazi character out of Germany for the story and then I heard this U-boat story - I thought oh, that would be possible to get someone away on a boat no one knew about and for a writer that's a 'wow' moment," Mr Harris said.
"I have had so much fun with this and came across so much fascinating history around these parts," he said.
Submarine U-862 initially sailed from Germany in May 1944 and four months later was in the waters of Japanese-controlled Malaya.
Commander Timm then headed for the waters of Australia, sailing down the western coast, across the Great Australian Bight and around Tasmania, then up toward the port of Sydney.
On Christmas Day, 1944, it sank the US liberty ship Robert J Walker - one of two freighters it sank.
To escape the pursuing Australian forces it headed across the Tasman and circled New Zealand seeking more ships to sink.
It was during that voyage it cruised close to the Napier shore.
The commander later told of seeing the seafront lights as well as people dancing.
Mr Trevathan said his fascination with the visit of U-862 was ongoing and he had set up a special historical society focused on it.
One part of that fascination is the firing of the torpedo at the Pukeko just out of Napier Port.
During a visit about 15 years ago a navy research vessel carried out several sonar sweeps of the area during a visit to Napier, but was unable to detect it.
Mr Trevathan said he hoped 21st century technology would one day finally locate its whereabouts.
As for the U-862, when Germany surrendered on May 8, 1945, it was put into Singapore and taken over by the Japanese as I-502.
After Japan surrendered it was scuttled in the Straits of Malacca.
