In Episode 8 of Netflix’s new season of The Crown, we see the queen make a potentially deadly error: she shares her opinion. Margaret Thatcher, Prime Minister of the United Kingdom, has managed to ruffle Her Majesty’s normally immovable feathers, owing in large part to the PM’s hesitation to accept sanctions against apartheid-tainted South Africa. Furthermore, Thatcher is not a fan of the Commonwealth, a group of countries dedicated to strengthening democracy and human rights, the majority of which are former British territories. The Commonwealth is dear to Queen Elizabeth II. As a result, they reached a dead end.

Thatcher was dubbed as “The Iron Lady,” during her 11 years in government from 1979 to 1990, another powerful woman at the helm of a country that had already seen the queen as its unwavering monarch for decades. In season 4, The Crown takes care to examine the interactions between the two exceptional ladies, who were just six months apart in age.

“There are a lot of similarities between them. Obvious ones like marriage, and kids, and faith,” Gillian Anderson told OprahMag. “But there are a lot of differences, too, about how they approach issues of the day. And so it’s quite easy to imagine how they might have not riled each other…but how there could have been some friction there along the way.”

Margaret Thatcher and Queen Elizabeth had a notably complicated relationship. A notorious 1986 report in the Sunday Times, headlined “Queen dismayed by ‘uncaring’ Thatcher,” was among the flashpoints in their time working together—understandably, because it claimed that the Queen, who has always tried to stay out of politics, strongly disagreed with the Prime Minister’s refusal to impose sanctions on apartheid South Africa. It further stated that Thatcher was “confrontational and socially divisive.”

Mrs. Thatcher was unique. She regarded herself as a maverick, a moderniser, pulling Britain into the 1980s kicking and screaming. She had vowed to change the paternalistic settlement that had dominated Britain’s political and economic life for the previous 40 years – a consensus for which the Queen herself had become a living symbol with her yearly addresses about duty and service. Moreover, although past Conservative prime leaders were frequently viewed as members of the upper-class establishment, Mrs. Thatcher, who defined herself as a “plain, straightforward provincial,” saw the establishment as the adversary.

One of the queen’s primary responsibilities is to hold Audiences, which are a “key element of the queen’s day-to-day work, and enable her to give time and focus to key individuals,” according to the official website. Throughout her reign, Queen has convened a weekly Audience with the Prime Minister in order to discuss governmental concerns.

The site states, “The Audience is held in an Audience room in her apartments and is entirely private.” “Though the queen remains politically neutral on all matters, she is able to ‘advise and warn’ her ministers — including her Prime Minister — when necessary.”

Much of the hostility between the two is said to have developed during these unrecorded sessions. According to the 2014 documentary The Queen and Her Prime Ministers, Thatcher was usually 15 minutes early, and the queen always made her wait.

According to CNN, their conversation was “professional, formal, and famous stiff,” and the prime minister saw the yearly trips to the Balmoral royal home as “interrupting her work” — and labeled their relationship “tense.”

“The audiences were rarely very productive because Mrs. Thatcher was nervous,” writes Charles Moore in his 2015 biography of Thatcher.

The two ladies come from quite different backgrounds. “Underneath Thatcher’s armour of self-belief and simple Grantham philosophies lurked deep insecurities, many of which were class based,” Palmer said. Queen Elizabeth belonged to the highest social class in England, and she acted, dressed, and behaved accordingly. Thatcher was the self-made daughter of an alderman, and as depicted in The Crown, she was not regularly exposed to blood sports or other affluent hobbies. Palmer stated that she “didn’t know how to treat the queen,” and that their upbringings had given them vastly different perspectives.

“Life was about pulling yourself up by your boot straps and making something of yourself with [Thatcher’s father],” Palmer wrote. “By contrast, the queen’s father, George VI, was determined to resist change in whatever shape it might appear; for him, maintaining the status quo was the highest virtue. These paternal philosophies would stick like glue to their respective daughters. To understand both women, you must understand the fathers.”