Meaning of Aplomb

His Lordship was in the study when the butler approached and coughed discreetly.

 
 "May I ask you a question, My Lord?"
  "Go ahead, Carson ," said His Lordship.
  "I am doing the crossword in The Times and I have found a word I am not too clear on."
  "What word is that?" asked His Lordship.
   "Aplomb," My Lord.
  "Now that's a difficult one to explain.  I would say it is self-assurance or complete composure."
  "Thank you, My Lord, but I'm still a little confused."
  "Let me give you an example to make it clearer.  Do you remember a few months ago when the Duke and Duchess of Cambridge arrived to spend a weekend with us?"
  "I remember the occasion very well, My Lord. It gave the staff and myself much pleasure to look after them."
   "Also," continued the Earl of Grantham, "do you remember when Wills plucked a rose for Kate in the rose garden?"
   "I was present on that occasion, My Lord, ministering to their needs.  
  "While plucking the rose, a thorn embedded itself in his thumb very deeply."  
 "I witnessed the incident, My Lord, and saw the Duchess herself remove the thorn and bandage his thumb with her own dainty handkerchief."
  "That evening the hole that the rose made on his thumb was very sore. Kate had to cut up his venison even though it was extremely tender."
 "Yes, My Lord, I did see everything that transpired that evening."
  "The next morning while you were pouring coffee for Her Ladyship, Kate inquired of Wills with a loud voice, 'Darling, does your prick still throb?'

And you, Carson, did not spill one drop of coffee!

THAT is "aplomb."

aplomb

[Button] noun \ə-ˈpläm, -ˈpləm\: confidence and skill shown especially in a difficult situation