SCRIPTS for The Crown had to be rewritten after producers failed to get Gillian Anderson back for her role as PM Margaret Thatcher.
Despite their best efforts the US actress was not for returning as Maggie, throwing the show into more chaos.
The upcoming series six of the Netflix royal drama has already become mired in controversy over how it will portray the 1997 car crash death of Princess Diana.
Anderson, 54, won an Emmy and a Golden Globe for her series four role as Iron Lady Maggie, famous for her “lady is not for turning” speech in 1980.
Scriptwriters hoped she would return to The Crown, scriptwriters had included Thatcher in an episode covering Queen Elizabeth and Prince Philip’s golden wedding anniversary.
A TV source said: “Gillian’s portrayal of Thatcher was met with global critical acclaim and she was a huge asset to The Crown.
“It had been hoped she would be able to make an appearance in scenes around the golden wedding but sadly that has not been the case due to scheduling issues.
“As ever with the series, clever scripting will mean viewers will be none the wiser.
“But it’s been another blow for producers in what’s already been a fairly dogged production.”
The exact diary clash behind Gillian’s decision is not known.
But the star spent time helping War Child with its campaign to help those caught up in the Ukraine conflict in February, when the scenes were being filmed.
The original script depicted the Queen and Philip sat on golden thrones in front of distinguished guests including Baroness Thatcher, Princess Anne and The Queen Mother for a 1997 dinner.
At the time the Duke of Edinburgh gave a highly personal speech on the secret of their long marriage.
Philip said: “The main lesson that we have learnt is that tolerance is the one essential ingredient of any happy marriage.
“It may not be quite so important when things are going well but it is absolutely vital when things get difficult and you can take it from me, The Queen has the quality of tolerance in abundance.”
The dinner was on November 19, just three months after the death of Diana
Instead, producers have shifted the action to a second dinner, originally held on November 20.
Viewers will now see Imelda Staunton, 67, recreate The Queen’s famous “strength and stay” speech about the Duke, who is portrayed by Jonathan Pryce, 75.
At the time Her Majesty said of her husband: “He has, quite simply, been my strength and stay all these years and I, and his whole family, and this and many other countries, owe him a debt greater than he would ever claim, or we shall ever know.”
Baroness Thatcher was not in attendance at that second dinner, negating the need for Anderson to appear for filming.
She dated The Crown’s showrunner Peter Morgan from 2016 until 2020 and they remain friends.
The Crown is one of the biggest shows produced by Netflix.
Since it began in 2016 the drama surrounding the reign of Elizabeth has been viewed on 73 million accounts around the world.
The programme was initially set to end after five series, however, due to demand and the complexity of the storylines a sixth and final series was added.
Claire Foy, Olivia Colman and Imelda Staunton have all depicted Her Majesty.
Representatives for Netflix and Gillian Anderson did not respond to requests for a comment.