The Buckingham Palace is a monumental site located in London, England. In real life, it is home to the monarchy, either King or Queen and currently to live in the building is Queen Elizabeth II who was crowned Queen in 1953. Buckingham Palace appears in Command & Conquer: Red Alert and Command & Conquer 3: Tiberium Wars.
Red Alert 1
In the non-canon Soviet campaign, the Soviets managed to defeat the last Allied forces at the English coast. Their forces marched into London and captured Buckingham Palace. Stalin celebrated the end of the war in this palace, only to be poisoned and killed by Nadia. Kane, in turn, betrayed Nadia and shot her in the back, proclaiming the player as the new chairman and that Kane "is the future".
By 2047, Buckingham Palace was no longer home to the British monarch. Like the White House, it had been relegated to being a symbolic Western monument under the protection of GDI. The palace was seen just that as such by the invading Scrin forces. When the aliens attacked London led by Foreman 371, they summarily defeated the GDI forces defending the palace and destroyed the palace in the process. The Parliament House and Big Ben suffered a similar fate.