The Duke of Sussex, Captain General Royal Marines, visited Marines in Norway to mark 50 years of Commando Helicopter Force (CHF) and Joint Helicopter Command deploying to Bardufoss.
Prince Harry arrived in a private plane and spent three hours at the base meeting service personnel.
In a nod to Valentine’s Day, Marines dug a fresh quincy and decorated it with candles and framed photographs of Prince Harry and Meghan’s wedding.
“You weirdos," he joked.
"It's very kind of you to invite me into your private shrine or whatever you want to call it. And the music, is that part of it? Romantic, isn't it."
Air Engineering Technician Burns, 36, from Inverness, said afterwards:
"We took him [the Duke] through the structure of the shelter, how it's made.
"He is used to the weather, I think, because he said about exercises he had been on, he looked around at the shelter with the pictures and candles and he said we were weirdos."
The visit was also the first time the Duke has publically worn the Royal Marine’s famous green beret since becoming their Captain General two years ago.
Bardufoss is located 200 miles (322km) inside the Arctic Circle and the Marines are there to take part in the annual Exercise Clockwork.
The exercise began in 1969 and since then has trained over 16,000 Royal Marines and Royal Navy sailors and airmen.
It is seen as vital by the military to ready the Royal Marines and Royal Navy personnel that form CHF for cold weather operations.
Military personnel are taught how to survive, operate and fight in the sub-zero conditions and gain experience of operating aircraft in severe cold weather and mountainous environments.
The multinational exercise, hosted by the Norwegian Armed Forces, comprises Environmental Flying Qualifications, Cold Weather Survival, Tent Group Commander and Snow and Ice Driving Courses.
During the Duke's visit, he was briefed on the history and context of Exercise Clockwork and he was also taken to watch outdoor ground training, the taking in of field tents and inspect snow vehicles.
Prince Harry also cut a birthday cake with a sword and thanked the Marines for their service:
"It's really nice to see you all and know you're having a good time out here. I think most of you would be somewhere else, Salisbury Plain or somewhere miserable, this gives you an opportunity to get out there and use every single day as an experience."
Warrant Officer 1st Class Adrian Shepherd, who has served with CHF for 27 years, said:
"This is the first time His Royal Highness has visited Joint Helicopter Command since becoming Captain General and it is great that he is doing the visit while we're in Norway.
"He was able to get a good look at what we do and how we operate in these harsh conditions. He saw the amount of training that goes into it and why it is so important that we do this exercise every year.
"It is good for the people out here to see their hard work recognised during a significant year for the exercise."
Following the royal visit, a Royal Navy Sea King MK4 will be presented as a gate guardian by the British military to the Norwegian Armed Forces to mark the 50th anniversary of Exercise Clockwork.
In 1969, the first Westland Wessex helicopters, of what is now CHF’s 845 Naval Air Squadron, arrived in Scandinavia and, lived out of rudimentary shelters.
They conducted trials to demonstrate Britain’s commitment to defend NATO’s northern flank and test their ability to support 3 Commando Brigade in the unforgiving environment.
In those 50 years, British military aviators have flown more than 40,000 hours in the Norwegian mountains.
For 2019, Apache attack helicopters of 656 Squadron, 4 Regiment Army Air Corps, have joined CHF helicopters for the first time.
Already as part of Clockwork, 847 Naval Air Squadron (NAS)’s Wildcat Battlefield Reconnaissance Helicopter has carried out underslung load training operations.
Three Mk3A Merlin helicopters from 845 NAS will also fly from Yeovilton over three days to join the exercise.
Once in Norway, engineers work in temperatures as low as -30°C to keep aircraft functioning and aircrew are tested in tasks involving night-time snow landings, mountain landings, troop drills and load lifting.