Few can put on a period drama quite like Julian Fellowes.

From penning the Oscar-winning Gosford Park to the multiple award-winning Downton Abbey, and all manner of success in between, the actor-cum-novelist-cum-director-cum-screenwriter has masterminded his position as the frontrunner when it comes to suspenseful, corset-laden drama.

His latest Sunday night fare is Belgravia, an ITV adaptation of his best-selling novel of the same name, which details a story of secrets and scandals amongst the upper echelons of London society in the 19th century.

“I am always interested in periods of great social mobility when things were changing,” explained Fellowes, 70, when we met on set.

“The years after the Battle of Waterloo leading to the beginning of Victoria’s reign were a time of tremendous change. The expansion of the British empire, the increase of certain industries, the beginning of empire trading and mill workers were suddenly expanding...” he lists.

“It is also the period when the railway was beginning and railways were making everything much more accessible, so the whole country was in a state of flux. And really, in essence, that is what the story of Belgravia is about - that and the characters within that context.”

OK, so what else is there to know?

THE SET-UP

The six-parter kicks off with a real historical event - the Duchess of Richmond’s ball on the eve of the Battle of Waterloo.

On one side you have the Trenchards, a middle-class family who are a part of developing Britain at the time; and on the other, you have the aristocratic Brockenhursts, who are part of ‘old society’.

When the Trenchards accept an invitation to the now legendary ball, it sets in motion a series of events that will have consequences for decades to come as secrets unravel behind the porticoed doors of London’s grandest neighbourhood.

“The image of all those young glamorous people dressed up and dancing and then a couple of days later half the young men dead - some still in the costumes they wore for the ball - is very powerful,” Fellowes muses.

“That contrast between great privilege and great tragedy.”

But at the heart of the story, moving forward, are two very different women in Anne Trenchard and Lady Brockenhurst, he reveals.

“I thought, ‘What can they have in common? How can I make it believable that they have a relationship?’ And it occurred to me that if they have a joint grandchild, that would make for a relationship they couldn’t escape from.”

“The story is based on secrets,” he confirms. “The audience needs to be constantly surprised. If there are no surprises, then a drama lacks energy.”

THE STARRY CAST

As expected with Fellowes, his stellar ensemble cast is not one to be scoffed at either.

While Green Wing’s Tamsin Greig will play the part of Anne Trenchard, James Trenchard will be played by Cranford’s Philip Glenister, and the brilliant Dame Harriet Walter (Sense And Sensibility) will take on Lady Brockenhurst.

“Producer Gareth [Neame] and I felt it was time to go beyond our village of the regular Downton Abbey actors, so to speak. So we set about finding new people,” he recalls.

“There are some actors in it, such as Harriet Walter, Philip Glenister and Tamsin Greig, who I have been a fan of for quite a long time and really wanted to get for Belgravia. And I had worked with Tom Courtenay before - in fact I directed Tom in my own script, Separate Lies, and we have been together in two or three TV films,” he remembers.

“But as always, the young actors are completely new for me and I am really pleased with them!”

Further cast members include Alice Eve, Tara Fitzgerald, Ella Purnell, Richard Goulding and James Fleet, among others. For the likes of Rada-trained newcomer Jack Bardoe, Belgravia is his first TV role.

THE TRENCHARDS

For Greig, 53, it was Fellowes’ decision to put two women centre stage that proved most compelling.

“He has focused on their power, which is that they have secrets about the continuation of the family line,” she reasons. “It’s what they do with that information which drives the story.”

And having Glenister as her on-screen husband?

“It’s been an absolute joy!” Greig admits. “He’s a brilliant raconteur, very funny. He’s really easy to be around and very playful, so that’s been a lot of fun.”

“We did a lot of laughing, which is not always good when you’re in front of the camera!” Glenister, 57, agrees.

“One day we were shooting a dinner party scene in a country house near Reading - it took all day to film it. I said to Tamsin, ‘This is insane. We’re all dressed up to the nines having a six-course lunch at 9.30am on a Tuesday morning when everyone else is going to work’.

“Tamsin replied, ‘Remember, we do get paid for it!’ ‘I know, don’t tell anyone!’”

THE COMPARISON

Will there be echoes of Downton Abbey in this production?

“People are entitled to compare the two [but] they’re not very similar. They are set in very different periods, for a start,” Fellowes reasons, Belgravia’s predecessor having focused on the turn of the 20th century.

“But they have some elements in common. For instance, if you were a strong and ambitious woman in 1840 or 1912, you had to find different routes around the rules. You had to be creative if you wanted to stay inside society while achieving what you wanted,” he notes.

“We all know that Julian can spin a yarn,” Greig adds.

“And just seeing this script, and also reading Belgravia, he knows how to keep you turning those pages, and to give you characters that, regardless of where they live in the hierarchy, you go ‘Oh, I recognise that’, or ‘That’s in me’.

“He’s very interested in human nature and is able to place human beings in any era that make you go, ‘That’s in human beings’. Not, ‘That’s really 19th century’.”

“I’ll just be very happy if people enjoy it,” hopes Fellowes. “But if every now and then something in the story prompts an extra thought on the way into work, that would be great too.”

  • Belgravia starts on ITV today, Sunday, March 15.