It was usually the strongest beer a brewery produced, only rivalled by the occasional Imperial Stout. Ranged between 8% and 11%. Unlike most styles, the strength wasn’t drastically reduced by two World Wars. Though they weren’t totally immune.
Barley Wine came almost exclusively in bottled form. Usually nips (third of a pint) or occasionally half pints. It wasn’t usually something you drank all night. More something to finish off a session with or to warm you up in the cold weather. As an advertisement for Bass No. 1 from 1938 claimed:
“BASS NO.1 BARLEY WINE The wine for warmth. Drink it regularly. It is your surest protection against colds and flu.” Daily Herald - Wednesday 16 February 1938, page 17.
I’m not sure anyone should be taking medical advice from an ad. I wonder how well No. 1 would have worked against corona?
This one didn’t make such ridiculous medical claims, though it did say it would keep you warm:
“THE WINE FOR WARMTH
One glass of BASS No. l BARLEY WINE keeps you warm for a very long time, and so you do not feel die cold as others do. Prove it now. One glass will convince you.” Yorkshire Evening Post - Tuesday 09 January 1934, page 8.
A further advertisement demonstrates that Bass No. 1 was one version which did sometimes turn up on draught:
“BASS' PALE ALE and No. 1 BARLEY WINE always on draught”
North Devon Journal - Wednesday 24 March 1937, page 6.
I can’t imagine it being sold in pints, though.