The Crown also stars Helena Bonham Carter as Princess Margaret, Erin Doherty as Princess Anne, Emerald Fennell as Camilla Parker Bowles and Marion Bailey as the Queen Mother.
“Season 4 of The Crown is out in November – I wonder if the time-travelling new Routemaster bus will also be in it?!,” one viewer tweeted.
The series also charts the growing tensions between Thatcher and the queen, as the prime minister leads the country into the Falklands War.
However, it was an image of Lady Diana Spencer, played by newcomer Emma Corrin, that attracted attention from eagle-eyed fans who spotted a historical mistake in the background.