Possible Clues:

• How William the Quaker got on the long way
• The long way to write No in French
• The long way to write No?
• That's a long way to write No for a streamer
• Write 'Neutral' on the flag
• Long to be flying for writing on it, by the sound of it
• Triangular or swallow-tailed flag
• Long to have it flying in a way to write No?
• No French following pound standard
• Long to write to the French, no?