Image copyright Getty Images

The US president-elect Donald Trump has German ancestry on his father's side - but his mother was Scottish. During the election campiagn BBC Newsnight's Stephen Smith went to the Isle of Lewis in the Outer Hebrides to find out more.

Lewis is a windblown, God-fearing outcrop notable for its Gaelic heritage, its peat, and its jealously guarded sense of propriety.

Trump's mother, Mary MacLeod, was born there in 1912, to Malcolm MacLeod, a fisherman, and his wife, also called Mary.

Young Mary left the island at the age of 18 for a holiday in New York, where she met a local builder by the name of Trump - and the rest, as they say, is histrionics.

While some journalists have been pursuing the juicy story of the property developer's German grandfather, who appears to have supplied hard liquor and showgirls to gold prospectors in the Wild West, I decided to concentrate on the more understated but deeply enigmatic narrative of his maternal line.

I was encouraged in this by Trump himself, who has spoken fondly of his Scottish roots, and even went so far as to make a characteristically hush-hush visit to Lewis in 2008, his airliner "Trump 1" scorching the heather around the catwalk-like runway.

He flew into the island for a grand total of three hours or so, as councillors were debating a controversial Trump golf resort, a solid 2-iron away on the mainland. (The course is in business, though he's cooled on it ever since he failed to block a nearby wind farm.)

At the time, he said: "I have been very busy - I am building jobs all over the world - and it's very, very tough to find the time to come back. But this just seemed an appropriate time, because I have the plane... I'm very glad I did, and I will be back again."

Image copyright PA

When our own twin-prop flight touched down in Lewis, I sucked in a lungful of rarefied northern air and began to grasp what the Trump family liked about the place.

It's perfumed by an intoxicating blend of kelp and nitrate-rich sod that would have the apothecaries at a cosmetics laboratory rending their white coats in despair.

At night, the sky's as clear as the small print on a Trump contract, and the stars seem close enough to touch.

Image copyright Getty Images

Perhaps it's this transparency - a sense that what you see is what you get - that accounts for their gruff rectitude. I'm reliably informed that Donald Trump is the talk of the place, but they won't necessarily talk about him to an outsider, on the charitable basis that if you can't say something nice about someone…

There's that, and there's also a formidable tradition of Calvinism, which has earned Lewis the TripAdvisor-friendly tag of "the last bastion of Sabbath observance in the UK".

This is such an established part of Lewis's reputation that the hostile environment specialists who brief BBC teams before assignments issued us with hipflasks. In fact, I found the pubs of Stornoway open til the witching hour even on a school night.

Retired healthcare worker Kathy McArthur told me, "When I first came here years ago, the swings were still padlocked on a Sunday so the children couldn't play on them. But now you see people out in the town with their children on a Sunday whereas it used to be just people going to church. There have been a lot of changes."

That said, I heard one outlying settlement described as a "religious village".

One thing that Trump has in common with adherents of the old religion on Lewis is that he takes the pledge. He does not drink. He suffered the horror of watching his own brother die of alcoholism, which reinforced whatever strictures he absorbed at his mother's knee.

Mary MacLeod was raised in the little village of Tong, among low-rise garrison-style homes "finished in pukey pebble-dash", as one Lewis writer puts it.

Who was Donald Trump's mother?

Image copyright Time & LIfe / Getty Images

Born 1912 in the small village of Tong on the Isle of Lewis

Father was a Gaelic-speaking fisherman

Met Fred Trump on holiday to New York - she emigrated and they married in 1936

Had five children and lived in a wealthy area in Queens, New York, and was active with charities

According to Donald Trump, she was religious and loved the Queen

Died in 2000 in New York aged 88

Trump's cousins still live in Tong, not far from the capital Stornoway. I was very firmly informed that no-one would talk to us. After I made my apologies and left, I tried to put my finger on what the experience reminded me of.

Perhaps I caught the family on a bad day, and no doubt they are weary of the world's press beating a path to their door, but it struck me that it had been like visiting the scene of a mortifying calamity. I hesitate to say it, but there was a sense of shame as well as irritation.

In a Stornoway pub, I recounted the experience to Ian Stephen, a storyteller in the island's age-old fireside tradition, and author of an acclaimed Lewis novel, A Book of Death and Fish.

"Oh yeah, I can imagine it. You would like to picture Donald with that lovely hair being caught by an island breeze and him helping to carry around a big basket. And what do you get instead? These outbursts of his - and everybody goes like that..." Stephen cradled his head in his hands in mock horror.

Image copyright Getty Images

"It's not fashionable, but in Lewis our main passion is a bloodsport… genealogy," he went on. "You know, 'Who are your people?' So we're very proud of the people who have an impact on the wider world."

"So you're proud of Donald Trump?" I asked.

Folk musician Gerry Blane said: "Personally I think Trump's behaviour is questionable. There's a lot of intolerance there and you would never see any of that on the island. People used to think of the island as being intolerant and it's not. There's a mix of religions here now and people are very open, very honest and very kind."