"Mother" is the Chief of Staff
"Uncle James" is the head of state,
"Maisie's house" is the UN building
"Fishing" is 'discussing nuclear limitations'>br> "Peeling Plums" is 'advising of invasion plans for country xxx
Message starts: "Mother and Uncle James are on their way to Maisie's house to peel some plums. After that they hope to go fishing, then see a movie. Have a lovely weekend. Cousin Sam"
Message is indecipherable without a code book.