Julian Fellowes, by his own admission, is a man haunted by "witty, elderly women".

Having conjured Downton Abbey's Lady Violet Crawley and Gosford Park's Constance, Countess of Trentham from the innermost recesses of his mind, it's very much a torment of his own making.

"I suppose that comes from having been brought up by a sort of phalanx of great aunts who always had something to say on every subject," announces Fellowes, 72, with a nod of recognition.

Reflecting on a writing career dotted with Bafta nominations and an Academy Award for Best Screenplay (Gosford Park), it's the Tory peer's latest project - 19th century period drama The Gilded Age - that has transported us to his study via an internet connection.

Set against a backdrop of ornate frames and classical paintings, the self-declared monarchist can be found discussing the "idiosyncratic hallmarks" of his own creations, noting that when it comes to aristocracy, he prefers "institutions that bind the country together, rather than those that split the country apart".

Renowned for crafting period dramas investigating the nuances of British high society - most notably penning every word of the award-winning ITV series Downton Abbey - Fellowes is once again set to immerse audiences in a world dripping with opulence and excess. There is, however, one key difference this time around.

Swapping the sweeping lawns of England for the frenetic bustle of America's East Coast, The Gilded Age nestles itself among the Queen bees of New York high society. Reuniting with Downton executive producer Gareth Neame, Downton Abbey feature film director Michael Engler, and Altered Carbon director Salli Richardson-Whitfield, it's no wonder then, that the series has been dubbed the 'US Downton Abbey'.

"The Gilded Age is an American story and it needed to have an American perspective," says Neame, 54, of the project.

"Downton was really about the decline of the aristocracy in a way; they're losing power and they're having to think about money... but in The Gilded Age, we're seeing the beginning of the American Dream, the industrialisation of America, and seeing how that created enormous fortunes."

Starring Sex And The City's Cynthia Nixon, Mamma Mia! and The Good Wife's Christine Baranski, Bridgerton star Harry Richardson, Gone Girl's Carrie Coon, and Meryl Streep's daughter Louisa Jacobson in her television debut, it's a series overflowing with recognisable names.

A story centred around a penniless Marian Brook (Jacobson) following the death of her father, moving in with her spinster aunts, Ada Ross (Nixon) and Agnes van Rhijn (Baranski), becomes her only option. Sitting atop New York's social pecking order, aristocrat van Rhijn is out to defend the values and traditions of old money.

However, the arrival of Bertha Russell (Coons) changes everything, as the wealthy socialite and her businessman husband attempt to buy their way into the upper echelons of society. A rivalrous era which saw new money pitted against old, the series highlights the ever-increasing wealth disparity in New York City.

"The real difference actually, was that [Americans] didn't go in for primogeniture - they didn't leave the bulk of their fortune to their eldest son, or even a chosen child, they always divided their money between their children," says Fellowes.

"Of course, that's why there were so many more heiresses from America than there were from anywhere in Europe, because in Europe to be an heiress, everyone else had to be dead."

With filming for the series delayed from March 2020 until October due to the onset of Covid, Nixon, 55, describes the return to the set as "an incredible gift" following a "time of tremendous isolation". Reunited with Baranski - the pair played mother and daughter as part of the 1984 Broadway play The Real Thing - the duo describe the somewhat unconventional on-set protocols that cemented the shoot as one for the ages.

"We lived in these little plastic cubicles off the soundstage," explains Baranski, 69, with a laugh. "We could go into our little plastic house, take off our mask - but had to put them on as soon as we left our little container. I just remember seeing people in these gigantic period clothes, sitting in plastic houses like you're zoo animals or something. It was very bizarre."

Unafraid of tackling prominent and divisive subjects including money, sexuality, power, and race, The Gilded Age addresses topics missing from many traditional history books. With Brook - described by Jacobson as a "radical" woman "yearning for something more" - crossing paths with aspiring novelist Peggy Scott (Denee Benton) en route to her aunts' home, the series delves into what social mobility looked like from the perspective of black Americans at the time.

Submersing herself in reading material in a bid to research the lives of black middle and upper class New Yorkers during the 1870s, Benton describes the experience as "like drinking water". Recalling how she learnt about the nuances of black life "that have largely been left out of the mainstream story-telling model", Benton says the reading recommended by Fellowes reinforced "what it really meant to operate as a black woman in white spaces".

Regularly referring to the characters he creates as his "children", Fellowes goes on to acknowledge the surface-level parallels being drawn between Downton and his latest on-screen project.

"It's like saying, 'Oh, this medical series has also got doctors'," announces Fellowes matter-of-factly.

"I don't spend my life worrying about whether Agnes is funnier than Violet. I thought Violet was a great creation - a joint creation of mine and Maggie Smith's. But I think Christine is terrific in this. So in myself, I've moved on.

"All I think you can ever do is make a programme or a movie or a musical that you want to see," he finishes. "And if anyone else wants to see, that's great. But that's my motivational rule."

The Gilded Age is on Sky and NOW