Evans was serving as a Coastwatcher when he helped co-ordinate a search-and-rescue operation involving John F. Kennedy and his crew.

For years, Evans’s identity remained a secret. Eventually, he shared his story in the men’s adventure magazine, Cavalier, in January 1961.

“I shook hands with the 35th president of the United States on a Pacific island in 1943,” he wrote.

“‘Man,’ he said, ‘am I glad to see you!’

“It was no glory-and-haloes stunt. It was just a routine job.

“For 17 years, I’ve kept my trap shut.”

An accountant from New South Wales, Evans was born in Sydney in May 1905. He had worked as assistant manager of a coconut plantation in Vanuatu, and with a shipping company in Solomon Islands.

When the Second World War broke out, Evans returned to Australia, intending to join the Royal Australian Navy.

“They were all braid and ho-hum then,” he wrote.

“They knocked me back cold.

“What use did they have for an old beachcomber like me, they wanted to know.

“So I said, ‘to hell with you’, and joined the army.”

John F. Kennedy and crewmen of the PT-109.  Back Row (L-R) Allan Webb, Leon Drawdy, Edgar Mauer, Edmund Drewitch, John Maguire, Lt. (jg) John F. Kennedy (standing, far right). Front Row (L-R) Charles Harris, Maurice Kowal, Andrew Kirksey, and Lenny Thom. Solomon Islands,1943. Photo: Courtesy John F. Kennedy Presidential Library and Museum, Boston

Evans landed at Guadalcanal in December 1942 and remained in the headquarters camp on the edge of Henderson Field until February 1943, when he made his way to Kolombangara Island, armed with radio equipment, a pair of binoculars, and a tommy gun.

“Think of an olive-green pyramid thrusting high out of the sea, 25 miles round, and covered with jungle,” he wrote. “That was Kolombangara Island.”

Working with locals, Evans set up and manned an observation post that afforded him a view of the island’s airstrip and sea approaches to the town of Gizo. He also collected information from local guides who acted as scouts, sharing what they had seen and heard.

In June 1943, Evans came up with a plan to relocate to the small island of Gomu, which would provide a better view of activity in the Blackett Strait.

He was planning to leave when he saw something in the water in the early hours of 2 August 1943.

“I spotted four Jap destroyers,” he wrote.

“One of them had put its searchlight on something floating in the water. I thought I saw the wreckage of a boat and figures moving on it.

“But in the darkness it was too far away to see properly, and I thought I was only imagining the figures. I sent my report to base immediately.”

Later that morning, headquarters contacted Evans.

“PT boat 109 lost in action in Blackett Strait. Crew of 12. Request any information.”

Evans waited for word from the scouts, reporting that there were “no survivors so far”, but that three torpedoes had washed ashore near the coastal village of Vanga Vanga.

“Headquarters’ next message came at 1.12pm,” Evans wrote. “But there was nothing definite to report for days. I had passed the news around and … there was nothing more we could do.”

United States Navy identification card for John F. Kennedy. Photo: Courtesy John F. Kennedy Presidential Library and Museum, Boston

After travelling to his new observation post at Gomu, Evans found one of his scouts awaiting him.

“I walked up to the old weatherboard house some trader had built and deserted,” he wrote.

“I heard the snap of a twig and whirled about with the tommy gun at the ready.

“But it was one of my scouts. Knowing that I was on my way to Gomu at a set time, he had gone there to await me.

“He had news. [The] men were on an island between Gizo and Ferguson Passage.”

Two men – Biuku Gasa and Eroni Kumana – had stumbled across the stranded Americans; Gasa showing Kennedy how to scratch a few words into the husk of a green coconut.

“Nauro Isl. Commander … Native knows pos’it … He can pilot … 11 alive … need small boat … Kennedy.”

Back on Gomu, Evans checked his charts, and wrote a message for the scout to deliver to the group, advising Kennedy to come to his position.

Kennedy examines the coconut husk he used for sending a rescue message in the South Pacific during the Second World War, Palm Beach, 1944. Photo: Courtesy John F. Kennedy Presidential Library and Museum, Boston

Later that night, rescue boats met Kennedy at the rendezvous point, exchanging a prearranged signal of four shots. Kennedy’s revolver was down to three rounds, so he borrowed a rifle from Evans for the fourth. Standing up in the canoe to give the signal, Kennedy did not anticipate the rifle’s recoil, which threw him off balance and dumped him in the water.

“I sent him off in the canoe, and he kept his rendezvous with the PT boat, led the rescuers, and got the survivors back to Rendova,” Evans wrote.

“And that, for me, was it. I never heard any more … How could I know he would become President of the United States? But I’m glad he made it. He was a nice bloke.”

Evans was awarded the Distinguished Service Cross for his “bravery and enterprise in reconnaissance operations” in February 1945 and was discharged from the Royal Australian Navy in May 1946.

Although the note Evans had written to Kennedy was kept after the rescue, his identity remained a mystery for the next 17 years as his name from the signature was often misread, and other details had been obscured during the war to protect his identity.

When Kennedy was elected President of the United States, he kept the coconut on his desk in the Oval Office. In an interview in February 1961, he confirmed that Evans was his rescuer, saying that he had gone unthanked “because I couldn’t read his handwriting”.

John F. Kennedy’s daughter, Caroline Kennedy, viewing Evans’s private records collection.