The Diplomat Is Back for Season Four—Where Is the Political Thriller Filmed?

The fourth season of The Diplomat opens with a bang—literally. In the first episode, US President Grace Penn, played by Allison Janney, survives an assassination attempt outside Windsor Castle. She becomes increasingly unpredictable afterwards, confusing her husband Todd (Bradley Whitford), Vice President Hal Wyler (Rufus Sewell), and Kate Wyler, the US ambassador to the UK (Keri Russell). The story brings the characters from Windsor Castle to Washington, DC to Lucca, Italy, where it concludes on a cliffhanger at a meeting of the G7.

Beech used some of the same locations and sets from past seasons, but also brought new locations to life in England, New York, and Italy. The interior sets were created at Steiner Studios in New York, while Wrotham House returned as Winfield House, the residence of the United States ambassador in London. Here Beech breaks down the key locations from The Diplomat Season 4.

The Diplomat. (L to R) Neil Pearson as Fitzwilliam, Allison Janney as Grace Penn, Rufus Sewell as Hal Wyler in episode 401 of The Diplomat. Cr. Nick Wall/Netflix © 2026NICK WALL/NETFLIX

Windsor Castle

Season 4 opens with an impromptu visit to Windsor Castle. As the envoy leaves the British royal residence to fly back to the US, President Penn gets shot by an unknown assailant. Beech combined nine different locations to create Windsor Castle and its grounds. The exterior and inner courtyard were filmed at Burghley House, while Belvoir Castle, Lancaster House and the British Foreign Office were used for interiors. Back in the US, the team filmed at Woolworth Estate, St. Josaphat Monastery Library and Sleepy Hollow Country Club. The grandiose panic room where Kate and Hal are locked down after the shooting was filmed in the crypt of a church on the Upper West Side.