BRITAIN made an embarassing protocol slip when it emerged that Queen Elizabeth II had congratulated Zimbabwean President Robert Mugabe on his country’s national day even as his supporters murdered a white farmer. The Foreign Office confirmed that a message of goodwill was sent to Zimbabwe on Tuesday, the 20th anniversary of independence. A spokesman said such messages were sent out to all countries on their national days, and are drafted by the Foreign Office and sent to Buckingham Palace for the queen’s signature.