Definition of an ocean liner

One of John Heald's groupies asked what exactly the difference is between an "Ocean Liner" and a "Cruise Ship" and in yesterday's blog, John got Peter Shanks from Carnival UK to come up with a 4-point definition of an ocean liner. 

The first three points are concerned with ship design and routes. It was the  fourth that I liked...

Only Cunard has ocean liners - absolutely everybody else has cruise ships.