I like to think I can be gracious in admitting my own mistakes. Today it's confession time.
One page of the Whitbread gravity book is filled with entries for Strong Ales. The date is the same, July 16th 1953, for all of them. As Zythophile commented yesterday, this is just after the coronation of Queen Elizabeth. I suspect this isn't a coincidence. The beers come from all over Britain and are in descending order by gravity.
A variety of different names are used, but Strong Ale, Barley Wine and Old Ale are the commonest. There are 7 Barley Wines, 5 Old Ales (plus an Old Timothy and an Old John), 26 Strong Ales, 5 with a royal theme (King's Ale, Prince Ale, Royal Ale), 2 with a university theme (College Ale, Audit Ale), and 10 others. I make that 57 in total. All but two - Bulldog Pale Ale and Felinfoel Strong Ale - are dark in colour.
Now for my confession. Until about 15 minutes ago, I had been very sure of the difference between Old Ale and Barley Wine. Old Ale was dark, Barley Wine was amber. Simple. And Barley Wine was stronger at 8-10% ABV to Old Ale's 4.5-7%. Strong Ale had always seemed a very vague term to me, but if pressed, I would have plumped for an amber beer of 6-8% ABV.
Let's take a look at the gravities.
Barley Wine: 1063.3 to 1078.9, 5.0 to 7.49% ABV Old Ale: 1062.1 to 1080.5, 5.5 to 8.66% ABV Strong Ale: 1043.3 to 1081.2, 3.68 to 7.4% ABV (If we remove two unusually weak Strong Ales it looks like this: 1059.4 to 1081.2, 3.68 to 7.4% ABV
So what is the difference between Barley Wine, Old Ale and Strong Ale? Take a look at the specs and tell me what you think.