Deep in the Lithuanian woods, beyond the ugly high-rises built by the communists outside Vilnius, lies Buckingham Palace. Not the real one, of course, but a recreation for television of the corridors in which Lady Diana rode her bicycle on the eve of her wedding, and the state rooms where the Queen dutifully turns off unnecessary lights.

The set designers have been busy. What was, a few months ago, a crumbling tobacco factory is now home to the cast and crew of ITV’s latest megadrama, The Palace. Definitely not by royal appointment, the production team chose Lithuania as an affordable location for what some will see as a small act of treason. Here are state rooms and Chinese vases, paintings, busts, candelabra and all the pomp you imagine lies at the end of the Mall. Old sewage pipes are now pillars lining red-carpeted corridors. Other pipes have been pressed into service as heaters, snaking over black plastic like big, fat, warm caterpillars. Although it is only October, it is already bitterly cold.

Not quite a soap, and certainly no drama-documentary, this is Dallas in the palace, with echoes of The West Wing. The writer, Tom Grieves, has hijacked a real building and fictionalised its inhabitants, creating what he hopes will be an irresistible alternative cast of royals. Just as in the real palace, the staff live in the building, making this like a glitzy, slightly paranoid hotel. Those within even refer to everything else as “on the outside”.

The series opens with the sudden and unexpected death, not of an elderly queen, but of a king. Unlike our own Charles, a young Prince of Wales, Richard (Rupert Evans), has to take on the top job years before he is ready, and it causes trouble all round. His mother, Charlotte (Jane Asher), is handed the royal equivalent of a P45. With the ruthlessness of royal protocol, she is never referred to as queen again. Richard’s fun-loving brother, George (a show-stealing performance by Sebastian Armesto), is like a big kid whose best friend can no longer come out to play; and of Richard’s two sisters, the elder, Eleanor (Sophie Winkleman), is green with jealousy, while the younger, Isabelle (Nathalie Lunghi), is an 18-year-old rebel who would like to be clubbing in Camden. Isabelle flounces, Eleanor schemes, George tries to keep smiling and Charlotte calls for a stiff drink. And that is just the family. As for the staff, one has a beans-spilling book deal, another is leaking to the press.

At first glance, the two fun-loving princes who suddenly lose a parent look familiar. According to Grieves, though, there was never any intention to draw parallels with the real royals. “I wanted to write a show about a woman working in the shadow of power, and thought about who it should be for ages,” he says. “Then I suddenly thought, what if this woman was working for the king? It all blossomed from there.

People talk about Wills and Harry, but I’ve always been baffled by that. I thought about them briefly, but, quickly, you startwriting for your own characters.”

The Palace aims to be fun. “It’s designed to be a treat,” says Grieves, who wrote Channel 4’s first cop show, The Ghost Squad. “I want it to be delicious, humorous, thoughtful, respectful and smart. I want people to enjoy it.” Certainly, it delights in tiny insights into real royal life. BBC1’s recent series Monarchy: The Royal Family at Work may have shown how things actually function, but The Palace finds humour in the reality. “You are funny, Simon,” Princess Eleanor says when her private secretary, Brooks, suggests a liaison. “We don’t do staff.” And who knew that a footman announcing the king’s mother to the king has to say, “Your majesty. Her majesty, your majesty”?

“We had a nanny once whose boyfriend was a cook at Buckingham Palace,” says Roy Marsden, who plays the king’s private secretary. “He said, ‘The only time it gets a bit iffy is when Prince Philip phones at 3am, after a big day, and says, “Hello, can I have my usual?” I have to schlep down to the kitchen, make baked beans on toast and cart them up to his room. He’ll be sitting up in bed, reading or doing letters, and I’ll go back to bed thinking, is the bugger going to phone again?’”

Patrick Jephson, private secretary to Diana, Princess of Wales, was the royal consultant. The Diana Chronicles by Tina Brown was his recommended reading for the cast. He also told them that the only way to understand the royal family is to think of them as aliens. “You’d like them to be just like everyone else, but they aren’t,” says David Harewood, who plays Brooks. “They’ve been brought up with duty, history, patronage, and they are a breed apart.” Coming and going in ballgown, tiara and Ugg boots (when the balcony scene was filmed, there was snow just out of shot), Asher says it has to be this way. “The whole setup relies on creating this difference. If we treat them like ordinary people, you lose the point.”

Just as Margaret Thatcher was the greatest fan of Yes, Prime Minister, you cannot rule out that Her Majesty, gin and Dubonnet in hand, won’t find the series irresistible. “I don’t know,” Asher says. “I think it’s more likely to be Horse of the Year Show, don’t you?”

The Palace starts tomorrow at 9pm on ITV1

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