What makes wine 'fine'?

It’s New Year, and that means: quiz time! Publications by the score have been setting festive brainteasers, and I don’t want JancisRobinson.com to go without, so here’s my 2016 quiz: 

• What is ‘fine wine’? 

There. Did you enjoy it? This may not be the longest quiz ever, but I reckon it’s a real poser. This very question was sprung on me a month or so ago by a former colleague, and it left me stumped. This was not his intention: he had recently joined the London wine-broking fraternity and was doing a bit of research on what this term means...