The beekeeper from Tuakau and the rest of the ninth British Everest expedition spent six months at Pen-y-Gwryd in 1952-53 testing oxygen masks and tanks, plotting routes, practising rescues and honing their climbing skills ahead of their assault on the world's highest peak. They must have also tested the ale as part of their all-important team bonding sessions.
That was not the end of Sir Ed's connection with the hotel. Until his death in 2008 he returned regularly for expedition reunions, held every five years on the anniversary of his ascent on May 29, 1953.
Reminders of the world's best-known New Zealander are everywhere inside the Pen-y-Gwryd. The walls are lined with photos from the Everest expedition and a display case in the "smoke room" is crowded with mementoes - including the rope used to hitch Sir Ed and Sherpa Tenzing Norgay together, an enamel mug immortalised in the famous portrait of Sir Ed after his descent, a New Zealand $5 note, an oxygen cylinder, Tibetan prayer flags and a chip of summit rock. Puzzlingly, the cabinet also contains a Peruvian shrunken head.
The head was there for purely practical reasons, Elwyn explained.
"It used to hang up in the corner, but people were always mucking about with it, so we put it in the cabinet instead," he said.
In another room, where Sir Ed would test his oxygen equipment while scaling a stack of chairs, Elwyn pointed out his signature on the ceiling. Dozens of famous guests, including celebrated mountaineers, actors and musicians, have left their mark at the invitation of past publicans.
The most famous guests who didn't sign the ceiling were the Beatles, Elwyn said.
The band was in its spiritual phase and passing through Snowdonia to visit a yogi in the Welsh town of Bangor, but the proprietor decided they just weren't famous enough.
A final reminder of Sir Ed is chained securely to a wall behind the bar, where a row of polished tankards is engraved with the names of each member of the 1953 expedition.
All guests aged 12 and under who walk up and down Mt Snowdon, and solemnly swear they did so without adult help, are honoured with a ceremony and a commemorative badge.
They are also allowed to drink from the tankard of their choice. Needless to say, they always choose the tankard engraved "Edmund Hillary".
Elwyn said a few Kiwis visited to pay homage to Sir Ed, others stumbled on the hotel by chance and were "pleased to bits" to find the connection.
However, as a patriotic Welshman, he was obliged to point out that Everest was named after a Welsh surveyor, George Everest; and that, but for a problem with his oxygen tank forcing him to turn back a day before Sir Ed's ascent, the expedition's Welsh deputy leader, Charles Evans, would have been the first man on top of the world's highest mountain.
Elwyn said he had met Sir Ed several times at the Pen-y-Gwryd.
"The first time I met him I told him my grandfather used to keep bees. He was impressed by that.
"But no, I didn't talk to him much. He's a huge guy, massive jaw, quite intimidating really. I'm quite shy, and why would he want to talk to a little Welshman?"