Possible Clues:

• In ordinary language
• Not in code
• Note pocketed by sweet little thing needing no deciphering
• Not in code, note hidden in cake
• Not in cipher
• Real nice playing in the Open
• Not using substitution, say, can rile badly
• 'Cake' includes 'bun' ultimately, in plain language
• Endless reliance could be redundant at Bletchley Park?
• Racine with pupil in coded form, and uncoded