After spending the last hour or so navigating London's early-morning traffic jams, followed by a string of charmless highways, the winding country lanes and rolling green fields along the Hampshire-Berkshire border make for a delightful change of scenery.
This sense of pastoral bliss is enhanced when we enter the sprawling, sheep-riddled grounds of Highclere Castle. Set in 2400 undulating hectares of park and arable land, 100km west of the British capital, it's no ordinary country estate. To millions of TV viewers around the world, this is Downton Abbey.
Dozens of filming locations have been used for this dashing Edwardian-era drama – whose last-ever episode is broadcast in Australia on April 18 – but Highclere is its beating heart, the home of the Crawley family and its array of servants and guests. Highclere's visitor numbers have boomed since Downton's screen debut in 2010 – providing a shot in the arm for the estate's previously struggling coffers – and I'm certainly not the only one humming the show's mournful, piano-fuelled theme tune (Did I Make The Most of Loving You?) on the gravel drive approaching this ravishingly handsome stately pile.
There has been a property here since the Middle Ages, but the building we see today – with its weathered sandstone and neo-Gothic turrets and towers – was designed in 1842 by Sir Charles Barry, the architect of London's Houses of Parliament. Barry's fingerprints permeate the castle's grandiose interior, not least its dark-mahogany, well-upholstered library – the first in a series of treasure-strewn rooms that visitors are free to peruse on a self-guided tour.
Roaming the castle, upstairs and downstairs, via its marble columns, gilded mirrors, oak staircases and oil paintings, you'll dovetail between fact and fiction, absorbing the history of Highclere – the seat of the Carnarvon family for over 300 years – glimpsing eclectic artefacts (including a desk and chair once belonging to Napoleon), while reliving your favourite Downton scenes. Photographs of Hugh Bonneville, Maggie Smith and co, in costume, are located in the very spots in which they filmed.
You can even get a helping hand from Jim Carter. Carson the Butler in Downton, he narrates a new guided app, though don't expect him to lead you to the servants' quarters. Because Highclere has a modern kitchen – the Carnarvons still live here most of the year – Downton's kitchen scenes were shot in a London studio.
I tour the old-fashioned way, browsing the information boards and cards, and listening to commentary from the knowledgeable guides. Situated in every room, they're accustomed to Downton-related posers.
"Some visitors do get confused between the show and real life," says Jeanette Ghareeb, a guide I encounter in the saloon – the castle's lavish, vaulted-ceilinged centrepiece. "I was in the drawing room once, talking about Lady Catherine (the American-born wife of the 6th Earl of Carnarvon) and one visitor was adamant that I'd got her name wrong. She insisted I meant Lady Cora. Her friends had to put her right."
Downton's plots were shaped by real events, from global ones, like the sinking of the Titanic and the Spanish flu pandemic, to the (occasionally scandalous) goings-on in England's aristocratic homes. "Do you recall the storyline involving Lady Mary and Kemal Pamuk, the Turkish diplomat?" asks Jeanette. "Well that was inspired by true events. It didn't happen here, though. That was on another estate."
The characters who've slept in Highclere's galleried bedrooms down the years are as intriguing as any penned by Julian Fellowes, Downton's creator, and a long-time friend of the Carnarvons. Both Lady Catherine, and Lady Almina – the 5th Countess of Carnarvon, who set up a hospital for wounded soldiers at Highclere in World War I – have been the subject of books written by the current (8th) countess, who blogs about life at Highclere (ladycarnarvon.com). Her books can be purchased in a Highclere gift shop bulging with Downton-flavoured mementos.
Before you go browsing, or for refreshments in the tearooms, don't miss the Egyptian exhibition in the castle's cellars. It celebrates the remarkable story of the intrepid 5th Earl of Carnarvon, and his friend, Howard Carter, who excavated the Tomb of Tutankhamun in 1922.
The Pharaonic pottery, tools and jewellery displayed at Highclere today were rediscovered, hidden between the castle's drawing and smoking rooms, by the 7th Earl and his butler in the 1980s.
Whatever you do, don't leave Highclere without ambling around, and snapping pictures of the gloriously leafy gardens (you can't take photographs in the house). Blessed with lakes, follies and woodland – including serpentine-branched Lebanon cedar trees – the picnic-friendly gardens were masterminded by Lancelot 'Capability' Brown. Georgian England's finest landscape gardener, he earned his nickname because he would tell aristocrats that their land had great 'capability' for improvement.
To mark this year's 300th anniversary of 'Capability's' birth, Highclere is running tours and lectures that will explore the 'English Arcadia' he created here.
Collette features Highclere Castle on two of its UK-based tours: England's Treasures and British Landscapes. Priced from US$2599 (AU$3443), these tours, spanning 9-12 days, run between April and November, but Highclere visits are only included on July 16, July 22 and August 26 (on England's Treasures), and May 29, July 29 and August 19 (on British Landscapes); gocollette.com
If planning your own Highclere trip, be aware it's only open to the public 65 days per year (in 2016, there are limited dates in April and May, then from July 10 to September 7). Tickets can be pre-booked online, but usually sell out fast. Walk-up tickets, available on the day, are also sold. It's £22 ($41) to visit the castle, exhibition and gardens; highclerecastle.co.uk
Steve McKenna was a guest of Collette
FIVE OTHER GARDEN GEMS ON THE 'CAPABILITY' BROWN TRAIL
STOKE PARK James Bond's round of golf with Goldfinger was filmed at this grand Buckinghamshire estate, which was landscaped by 'Capability' Brown in 1750; stokepark.com
BLENHEIM PALACE Beguiling walking trails course through the lake-endowed gardens of this, the Oxfordshire birthplace of Winston Churchill; blenheimpalace.com
CHATSWORTH HOUSE Scenes for the 2005 adaptation of Pride & Prejudice, starring Keira Knightley, were shot at this lovely Peak District estate; chatsworth.org
ALNWICK CASTLE 'Capability' crafted the oak-and-beech-speckled gardens hedging the Northumberland castle that doubled up as Hogwarts in the first two Harry Potter movies; alnwickcastle.com
PETWORTH HOUSE Hundreds of fallow deer roam the rustic parkland by this stately West Sussex mansion; nationaltrust.org.uk/petworth-house-and-park