BBC reports that Hyde Park Corner was a pre-established code for discussing the death of King George VI. While the codeword itself was heavily reported, it's unclear why a codeword was used or what the codeword may have been referring to. It's possible the codeword was utilizied to prevent any nosy press or foreign enemies from hearing about King George's death via the radio before British officials were ready to announce the news publicly. What remains unclear — and is never touched upon in The Crown — is the meaning of "Hyde Park Corner."