The fifth season of “Downton Abbey” doesn’t begin airing until Sunday, but Pat Alford and sister Judy LeBlanc already know what happens. They caught the first episode when it aired in London in the fall. They also got an exclusive tour of Highclere Castle, where the PBS Masterpiece hit is filmed.

And, to paraphrase the old saying that “your home is your castle,” the home of the Eighth Earl of Carnarvon George Herbert and wife, Fiona, actually is a castle.

“When you’re driving up … your heart just starts beating faster and faster as you drive through the gate,” says Alford.

The imposing Victorian castle is set amidst a 5,000-acre country estate on the West Berskshire-Hampshire border in the south of England. “They (the owners) live in the house, except during the summer when it’s on tour,” says Alford, who actually got to meet the Earl as they were walking the grounds. “He was very nice.”

“You’d never know he was the owner,” adds LeBlanc.

The Earl and Lady Carnarvon move into a cottage on the grounds when the castle is open for tours. It’s where they were living in 2009 because of the crumbling condition of the castle — only the ground and first floors were usable. They credit the popularity of “Downton Abbey” and the tourists it brings with allowing them to begin much-needed the multi-million-dollar repairs.

Alford and LeBlanc made the trip in September with an exclusive tour group out of Baltimore.

“We saw everything!” Alford says. “Every room was spectacular … just like on TV, and the views of the rolling land. It was just breathtaking.”

Alford’s favorite room was the library.

“It’s huge, beyond words,” she says. “That room alone is worth the trip.”

The library is actually a double library and home to more than 5,650 books, the earliest dating from the 16th century. And, just like the fictional Crawley family, the earl and his family use it a great deal to gather before and after lunch or dinner. One of the favorite spots to sit is on the red velvet triple-camelback sofa.

“I just had to see that red sofa,” says Alford. “We snuck away from the group and took my picture sitting on it … I could have taken my suitcase and just moved into that library.”

LeBlanc’s favorite room was the grand saloon.

“It has a magnificent fireplace and multiple seating areas,” she says. “You see it in just about every episode of ‘Downton Abbey.’”

The saloon is the physical and social center of the castle. It was designed for the fourth Earl of Carnarvon in a Gothic style with rich decoration and completed in the 1860s. The wall coverings are made of leather brought back from Cordoba, Spain, by the third earl and date from 1631. They were hung here in 1862.

As they toured the house, guides talked about the filming of “Downton Abbey.”

“Nothing is changed,” says Alford. “Everything you see on the show is all theirs (the earl’s family) furniture. They may move a table to another side of the room, but there are no major decorating changes. Everything stays where it is.”

“They told us about how difficult it is to film in such tight quarters,” adds LeBlanc. “It’s all filmed right there except for the kitchen scenes. They’re filmed on a separate set.”

“We saw everything you see on the TV show and more,” says Alford.

They even got to live a little bit of the posh life by enjoying a luncheon in Highclere’s formal dining room.

“I sat at the head of the table under that magnificent Van Dyck portrait (of Charles I),” says Alford, who is still excited by the memory.

“They served us just like they do the family on TV … very formal, just like you see on the show,” says LeBlanc.

The tour of Highclere was the finale of the trip, which in addition to the watch party of the first episode of Season 5, also included dinner with Jessica Fellowes, niece of executive producer Julian Fellowes. She is the author of three coffee table books detailing the filming of the series. Alford and LeBlanc were seated at the table with Fellowes, who introduced her just-released book to fans that evening.

“She gave me her autograph to put in my copy once I got home and could buy one,” says Alford.

The women also came home with Highclere Castle scarves, part of a gift package they received after lunch at the caste.

“It was a very special trip … gives me goosebumps just thinking about it,” says Alford.