Possible Clues:

• *Composure metaphor in a P.G. Wodehouse title
• Calm courage
• It is kept by stoics
• Fortitude in adversity
• Comp claim from a courageous trumpeter?
• Symbol of resolution in bad times
• Terribly British attitude?
• Quality of stoicism
• Very British stoicism
• Seeing spreading purple on corpse, a copper shows self-control