I was so far in understanding that lavatory and toilet are synonyms. But they are different in the following passage of Jeffery Archer’s “Be careful what you wish for.”
A mastermind of IRA related gangster, MacIntyre give the direction to his underling, Brendan in a newly commissioned luxury liner, which they plan to destroy on its maiden voyage:
“Can you remember where the public toilet on deck six is? - - It’s on the far side of the first–class lounge. And by the way old chap, it’s a lavatory, not a toilet, That’s the sort of simple mistake that could get me caught out. Don’t forget this ship is typical of English society. The upper classes don’t mix with cabin, and the cabin classes wouldn’t consider speaking to those in tourist.” - Page 439.
However, COD (10th ed.) defines toilet as “(1) a large bowl for urinating or defecating into typically plumbed into a sewage system,” and lavatory simply as “= a toilet.”
OALED defines toilet as “(1) a large bowl attached to a pipe that you sit on or stand over when you get rid of waste matter from your body, and (2) a room containing a toilet,” and lavatory as “(1) a toilet, or a room with a toilet in it.
Both COD and OALED seem to suggest 'toilet' and 'lavatory' are same.
Is lavatory so different from toilet in actual usage as the character of Jeffery Archer’s fiction, (or Archer himself) recognizes?