It's 1997 and Tony Blair (MICHAEL SHEEN) is the newly elected Prime Minister of Great Britain, a point of happiness for his wife Cherie (HELEN McCRORY) who has a disdain for the royal family. Yet, as protocol dictates, she goes along with her husband to meet Queen Elizabeth II (HELEN MIRREN), a leader whose life operates entirely around protocol and who's been in her position of power and influence since the days of Winston Churchill.
Their roles and relationship are put to the test months later following the untimely demise of Princess Diana in Paris. Her ex-husband, Prince Charles (ALEX JENNINGS), wants to fly there to accompany her body back to England, but the Queen forbids it, citing protocol and the fact that the late Princess hasn't been part of the royal family since their divorce.
Her mother, the Queen Mother (SYLVIA SYMS), and husband, Prince Philip (JAMES CROMWELL), agree, but public sentiment soon turns from grief over Di's death to outrage that the royals haven't made any sort of public showing of sadness and are still vacationing at their Balmoral estate.
Thinking she's doing the right thing and that she knows the British people better than anyone else, the Queen refuses to alter their official response. As the public outrage grows, however, the Prime Minister decides he must intervene and try to convince her to change her mind, not only for the monarchy's reputation, but also for the good of the entire country.