Royston explained that Frogmore Cottage provided the couple with police security due to its location on the private estate around Windsor Castle, which protected them from press intrusion, royal watchers, and even terrorist attacks or assassination attempts. Losing Frogmore would mean severing a major tie between them and Britain, making return visits to the country more complicated.
Royston added that if the couple wanted to benefit from police protection around their residence, they would likely have to negotiate a room at another royal residence, making them more dependent on the wider Royal Family and palace institution. On the other hand, if they stayed at a hotel, they would be left with their private security, and it would be easier for members of the public and potentially journalists and press photographers to access them.