Copplestone Court, the elegant, eighteenth-century country home of Henry and Clarissa Hailsham-Brown, set in gently undulating hilly country in Kent, looked especially attractive in the moonlight which illuminated its facade on a clear, chilly evening in March.

"Exit Clarissa mysteriously," she declaimed in a dramatic stage whisper as she disappeared into the recess, a split second before Henry ushered the Prime Minister into the drawing-room.