The ITV series is due to return to our screens later this year for a fifth series but Fellowes has admitted the show cannot 'go on forever'.
In an interview with the Wall Street Journal, he revealed he has been commissioned to write a new US drama called 'The Gilded Age' but says he can't start work on it until 'Downton' has ended.
“When those families descended on New York, they took over.”
But he reassured fans that there would definitely be another series of Downton but also suggested it may be the last.
“I don’t know yet if there is a season six but it’s not going to go on forever. It won’t be Perry Mason.”
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