DESPITE having success in other TV and film projects such as spoof documentary Twenty Twelve and Shakespeare adaptations, The Hollow Crown – Hugh insists nothing could dull the excitement of returning to the set of Downton Abbey.

EVERYWHERE he goes Hugh Bonneville gets buttonholed about Downton Abbey.

The 50-year-old has been playing Robert Crawley, Earl of Grantham, since the show began in 2010 and has been left astonished at how popular it has become.

It is now watched in 250 countries and has won Emmys, a Golden Globe and a BAFTA.

The fifth series of the period drama, which also stars Dame Maggie Smith, Michelle Dockery, and Elizabeth McGovern as Robert’s wife Cora, gets under way tomorrow with the action set in 1924.

And once again Hugh will be at the centre of the action, both on and off screen.

He said: “It’s been quite interesting: a lot of the crew on The Monuments Men (a film he starred in this year with George Clooney) were avid fans.

“I was filming Downton and Monuments Men at the same time, going back and forth from one set to the other. One of The Monuments Men producers virtually pinned me to a wall asking ‘So what did you shoot last week?’

“It is fascinating how people get hooked on it.

“When you hear of people like John Kerry (the current US Secretary of State) saying he had insomnia and picked up a DVD his wife had been watching at 4am. He was still sitting there at noon, absolutely hooked on it, so it’s quite strange.

“You realise that an astonishing spread of people, from the guy on the street to someone running the foreign policy of an entire country, are responding to the material we’re making.”

George Clooney, who became a friend during the making of The Monuments Men is another high-profile fan of the show and there are rumours that the Hollywood star will appear in a charity episode of Downton for Text Santa later this year.

He will cameo as an American guest at the Crawley wedding in a sketch also starring Hugh and Michelle, who plays Lady Mary.

Despite early roles playing bumbling characters like Bernie in Notting Hill and Mr Rushworth in Mansfield Park, as well as a BAFTA nomination for Iris, Hugh has no doubt how important Downton was for him and for all the cast.

Last month he unveiled his £150,000 wax figure at Madame Tussauds placed among A-listers Kate Winslet, who he appeared with in Iris and George Clooney, his director in The Monuments Men.

Hugh said: “There is no question that Downton has opened doors for all of us.

“I would not have done The Monuments Men or Paddington, which we shot last autumn, without having done Downton.

“It’s been a calling card for so many of us.

“Michelle’s made a movie with Liam Neeson and Sophie (McShera, who plays assistant cook Daisy) and Lily (James, who plays Lady Rose) filmed a version of Cinderella directed by Kenneth Branagh.

“It’s hilarious to see how we all go off in our downtime, and come back with stories of adventures.

“So it’s been an amazing blessing for us all, it really has.”

As well as Downton, Hugh has showed his funny side in spoof documentary Twenty Twelve and follow-up W1A in March this year. A new series of W1A starts filming early next year. He has just finished filming a guest appearance in American fantasy series Galavant playing Peter the Pillager, a pirate king.

Hugh will also join Benedict Cumberbatch and Dame Judi Dench for the second run of the Shakespeare adaptations, The Hollow Crown.

Hugh will play Humphrey, the Duke of Gloucester in Henry VI Parts 1 and 2.

But success in other film and TV projects doesn’t dull the excitement of Downton Abbey for Hugh and the rest of the cast.

They are still thrilled to return every six months to film another of the award-winning series created and written by Julian Fellowes.

They return to “my second home” as Hugh calls Highclere Castle in Hampshire, which doubles as Downton Abbey, and Ealing Studios where sets of the kitchen and servants’ quarters have been built.

Hugh still approaches each new series with a mixture of nostalgia and excitement. He said: “I was doing a scene with Brendan Coyle the other day in the dressing room and I said, ‘I can remember the very first one we did in this room, in this set’.

“It seems extraordinary the momentum of the show has continued and we’re still getting bigger audiences.

“The bar is still set very high and the pleasure of reading the scripts hasn’t changed.

“Each season, with Julian’s writing, there’s a fresh detail of the character you didn’t know was there. He’s always surprising you.

“Everyone has shades, everyone’s contribution to the world of Downton has got many different facets.

“It’s easy to write the characters off or to pigeonhole them but he’s always reminding us that everyone has three dimensions.

“And that does keep it fresh.”

It’s not just the cast and crew who are immersed in the Downton world.

Their extended families have also been part of its phenomenal success.

Hugh, who has been married to wife Lulu since 1998, said: “When the show first started, my son Felix was seven and now he’s 12.

“For half his life, Downton Abbey has been the thing his dad does.”

There is much drama in the fifth series with a fire ripping through Downton and the modernisation of the estate a further burning worry for the man of the household.

Hugh said: “Robert realises he’s got to modernise or die but he won’t just tear up the landscape and build housing estates; he wants to make sure it’s done with a degree of sympathy for its history.”

* The new series of Downton Abbey starts on Sunday at 9pm.