This drama follows the political rivalries and romance of Queen Elizabeth II's reign and the events that shaped the second half of the 20th century. The fourth season covers the time period between 1979 and 1990, is set during Margaret Thatcher's premiership, and introduces Lady Diana Spencer.Episode 01 – Gold StickAs Elizabeth welcomes Britain's first woman prime minister and Charles meets a young Diana Spencer, an IRA attack brings tragedy to the royal family.Episode 02 – The Balmoral TestMargaret Thatcher visits Balmoral but has trouble fitting in with the royal family, while Charles finds himself torn between his heart and family duty.Episode 03 – Fairy-taleAfter Charles proposes, Diana moves into Buckingham Palace and finds her life filled with princess training, loneliness, and Camilla Parker Bowles.Episode 04 – FavouritesWhile Margaret Thatcher struggles with the disappearance of her favourite child, Elizabeth re-examines her relationships with her four children.Episode 05 – FaganAs Thatcher's policies create rising unemployment, a desperate man breaks into the palace, where he finds Elizabeth's bedroom and awakens her for a talk.Episode 06 – Terra NulliusOn a tour of Australia, Diana struggles to balance motherhood with her royal duties while both she and Charles cope with their marriage difficulties.Episode 07 – The Hereditary PrincipleGrappling with mental health issues, Margaret seeks help and discovers an appalling secret about estranged relatives of the royal family.Episode 08 – 48:1As many nations condemn apartheid in South Africa, tensions mount between Thatcher and Elizabeth about their clashing opinions on applying sanctions.Episode 09 – AvalancheCharles is caught in a deadly avalanche, prompting both him and Diana to re-evaluate their commitment to their troubled marriage.Episode 10 – WarAmid a growing challenge to her power, Thatcher fights for her position. Charles grows more determined to separate from Diana as their marriage unravels.