Wilson, "a genuine Irish draught horse", looks suitably huge (at 17 hands) – and suitably terrifying.
Though, to be honest, he's not as terrifying as the indemnity form I've just had to sign before hauling myself high into his saddle.
Was I comfortable galloping, it read. Cross country eventing? Negotiating water jumps?
For some reason, there's no box on the indemnity form that I could answer positively, such as, "Have all of your previous equestrian adventures ended in disaster?" I could have ticked that.
"Don't worry," Brighid, our instructress at Castle Leslie's stables in Ireland's beautiful County Monaghan, explains. "We'll just be going off for a wee toddle."
There's a little confusion after I finally clamber aboard Wilson and ask Brighid whether I should be riding "balls down".
For some reason she and her boss, Jenny, giggle uncontrollably (thank God they don't spook the horses).
But we finally work out that the balls of my feet need to be sharp to the stirrup, leaving my heels pointed down to ensure absolute control.
Not that Wilson cares. He knows who is in charge on this hour-long ride through the woods, puddles of mud, and aroma of wild garlic. And it's not the idiot in the saddle.
The Leslie family has been associated with horses for at least 1000 years. Around the time William the Conqueror landed at Hastings, Bartholomew Leslie rescued Margaret, the future Queen of Scotland, from drowning thanks to his mid-stream intervention on horse-back.
In gratitude, King Malcolm approved Leslie's marriage to his sister, Beatrice (courtship was easier in those days).
The family motto – "Gripp Fast" – is the instruction Bartholomew gave Beatrice as he pulled her out of the rampaging torrent.
Six centuries later, in 1644, their descendant Bishop John Leslie (known as "the Fighting Bishop" because of his battles against Oliver Cromwell's invading Roundhead army) purchased a house overlooking Glaslough ("green lake" in Irish).
Since then, Castle Leslie has been associated with a host of misfits from Winston Churchill to Mick Jagger, Jonathan Swift to Mrs Maria Fitzherbert – the secret Catholic wife of King George IV.
Talking of misfits, Castle Leslie was really put on the 21st-century map when Paul McCartney married his second wife, Heather Mills, in a marquee down by the green lake in June 2002.
Naturally, the McCartney menu was totally vegetarian but the "greenie" atmosphere was spoilt by the private helicopters dodging the paparazzi cordon.
The world's press had been tipped off by the late "Disco duke", Sir John (Jack) Leslie (the fourth baronet, then in his 80s). Jack had let slip to some of his closest new reporter chums in the village pub that McCartney would be marrying "next Wednesday", before adding "but I have to keep it secret".
A POW for most of World War II, Irish, proud and gay (homosexuality wasn't decriminalised in the Republic until 1993), Jack had dreams of turning Castle Leslie into a dancing venue in the 1970s, when Jagger was photographed checking out the venue.
Undeterred, the Disco duke continued to dance every weekend for much of his 90s – either in Ireland or Ibiza. He died in 2016, aged 99, having (to paraphrase Marc Bolan) "danced myself out of the womb…(and) danced myself into the tomb".
The strange thing is that Castle Leslie was a romantic wreck at the time of McCartney's wedding. Its re-emergence is solely due to Jack's niece, "Sammy" Leslie – a dyslectic globetrotter who has achieved miracles since she took responsibility for the Irish family estate in 2004.
The house itself is now superbly restored, as are the extensive gardens and grounds. The former hunting lodge (where I'm staying) has been redesigned as boutique accommodation, with a bar and restaurant (open to the public).
There's a cooking school, an upmarket spa, running tracks and one of Europe's top horse riding schools (hello, Wilson!).
Not that Uncle Jack or Sammy are exceptions to the Leslie family mould. The Leslies have always been an eclectic bunch, explains our guide, Owen McNaughton.
Look through the family tree and you'll find painters, writers, a big game hunter, a UFO advocate and a collection of strong, independently-willed women.
McNaughton is coy about his age, but admits, "I've worked here, in one form or another, all my life. My great-grandfather drowned in the green lake: suicide. They were tough times. He left a wife and young children behind."
"The Famine Wall" – built around the estate by the widowed Christina Leslie in the 1840s to keep workers employed during Ireland's Potato drought – still exists: a wall of inclusion, not exclusion.
McNaughton's current title is "concierge", though he's really the chief greeter and tour guide. And the first thing he tells us is that Castle Leslie is not a castle.
It's a stately home, he says – the third house built on this site: finished in 1878, and designed by the then owner, another John Leslie, the first baronet – a very talented gentleman artist who wanted to maximise the views of the green lake while building a house that could contain the artworks he and wife Constance had acquired during their years living in Italy.
Paintings, statues, precious works abound. But most visitors regard Castle Leslie's greatest treasure as Winston Churchill's christening gown, displayed in the drawing room.
Yet Churchill is loathed in this Catholic-dominated republic, so did it get here – and remain here?
Winston's American mother, Jennie Churchill, was one of three daughters of the mega-wealthy New York financier Leonard Jerome who instructed them to wed impoverished British noblemen.
Jennie married Lord Randolph Churchill (and enjoyed affairs with various lovers, including the future Edward VII). Her younger sister, Leonie, married a fourth John Leslie (the second baronet) and Jennie gave Winston's christening gown to Leonie on the birth of Shane Leslie, her first son.
Winston Churchill never visited Castle Leslie, McNaughton admits, but he did prove crucial in saving it.
During the Treaty negotiations before the formation of the Irish Free State in 1922, Churchill (British Secretary of State for the Colonies) asked Michael Collins, the Irish leader, "to spare my Aunt Leonie's house".
At the time, the IRA was setting fire to Irish stately homes owned by British absentee landlords. Collins was assassinated by the IRA but the pledge was kept.
Had Castle Leslie been torched, its magnificent library would be no more.
McNaughton tells us that in the 1740s, Swift (author of Gulliver's Travels) visited the previous house and commented, acidly, that he was surrounded by "rows and rows of books…written by the Leslies, all about themselves".
It's that kind of family, and that kind of "castle".
Cathay Pacific flies from Australia to Dublin four times a week, via Hong Kong. See cathaypacific.com
Castle Leslie is a two-hour drive from Dublin airport (public buses run from Dublin to Monaghan, a 14-minute taxi ride from the castle).
The heritage-listed castle rooms (such as the Mauve Room, which has hosted European royalty) evoke a different aristocratic era.
But most guests might prefer the 29 exquisitely furnished rooms of the Lodge (each named after a horse!).
Alternatively, opt for the self-catering Old Stable Mews (near the lake) or the village cottages in Glaslough. See: castleleslie.com
The Lodge offers Irish country cooking at Conor's Bar or fine dining at Snaffles. But if you just have one meal here make it the traditional Irish afternoon tea at the castle itself (exquisite sandwiches, cakes, scones and jams with a glass of champagne and bottomless pots of tea).
Steve Meacham travelled as a guest of Cathay Pacific and Tourism Ireland.