The series will be available from November 15.
A new trailer for series four of Netflix drama The Crown has been released which teases the arrival of Diana, Princess of Wales.
The clip, which was posted on the programme’s official Instagram page, also announces the arrival of former prime minister Margaret Thatcher, who is being played by Gillian Anderson.
Series four, which is set towards the end of the 1970s, will show Queen Elizabeth trying to protect the line of succession by finding a suitable wife for the Prince of Wales.
It will also tell the story of his early relationship with Diana and the trailer appears to contain a shot of her in her wedding dress.
Diana is being played by Emma Corrin, 24, and the series also features Josh O’Connor as Charles and Olivia Colman as the Queen.
The drama will also depict rising tensions between Mrs Thatcher and the Queen in the lead-up to the Falklands War.
At the beginning of the trailer, the Queen says: “Something as important as the monarchy simply cannot be allowed to fail.”
It also features shots showing Diana facing packs of photographers.
A post on the programme’s Instagram page said: “The monarchy. Above all else.”
Corrin is playing Diana in series four before Elizabeth Debicki takes over the role for series five and six.
Earlier this year, Ted Sarandos, chief content officer at Netflix, praised the series, saying: “73 million households around the world have made The Crown part of the global cultural zeitgeist.”
Netflix has previously announced that the programme will end after its sixth series.
The fourth series of the hit drama will launch on the streaming platform on November 15.