The real-life castles behind ‘The Diplomat’ have some eye-watering figures attached

Netflix's ‘The Diplomat’ returned for its fourth season and featured British properties that helped create the show's royal setting.

While Burghley House in Lincolnshire was used for exterior shots of Windsor Castle and Belvoir Castle in Leicestershire provided the setting for Hal's office scenes, viewers may be wondering how much these historic properties are actually worth. A new study, conducted by property information site Property Buyers Today, examined publicly available financial records and land data to determine the value of the two historic properties.

The research found that neither has a publicly available market valuation covering the entire property and its associated assets, but their financial records show the value of different parts of the estates. Burghley House, which was used for exterior shots of Windsor Castle in the fourth season of ‘The Diplomat’, has an insurance figure of £430 million covering the house, grounds, and chattels, according to the Burghley House Preservation Trust's audited accounts.

This represents the estimated cost of reinstating the insured assets, rather than their market value. The house itself and Burghley Lake are not assigned a capital value in the Trust's financial statements.

The accounts instead report a fair value of £124.1 million for the estate's let residential, commercial, and agricultural properties. This figure relates to the investment properties rather than the entire historic estate.  

Belvoir Castle does not have a public valuation for the castle, its contents, park, and gardens as a whole. A modelled estimate based on the estate's stated 15,000 acres and 2025 regional farmland values puts the land alone at between £109.8 million and £129.8 million.

However, this is an estimate rather than a formal valuation, and excludes the castle, other buildings, woodland, sporting value, and development potential. Saif Derzi, Founder of Property Buyers Today, commented on the findings: “The popularity of historic properties like Burghley House and Belvoir Castle extends well beyond their appearances on screen.

“Burghley attracted more than 144,000 paying visitors in 2025, while Belvoir welcomed over 83,500, with visitor numbers at the latter rising by 13% in a year. With both properties appearing in The Diplomat, it's interesting to look beyond their on-screen grandeur and examine what their financial records actually tell us. 

Historic properties like Burghley House and Belvoir Castle are difficult to value in the same way as typical residential properties. In these cases, the available figures offer insight into parts of the estates.”