As an expert sommelier and brewer, I understand that finding specific beer styles like barley wine can sometimes be challenging, especially in more traditional pubs. However, there are alternatives that can be used as substitutes to achieve a similar flavor profile. One such substitute is extra stout beer.
Extra stout beers, like Guinness Extra Stout, can be a suitable replacement for barley wine in recipes. While they may not offer the exact same characteristics, their rich and robust flavors can complement dishes in a similar way. The dark roasted malts in extra stout beers contribute to a deep, malty flavor with hints of chocolate and coffee, which can add depth to recipes calling for barley wine.
It's worth noting that the recipe you mentioned was written in the 1970s when Gold Label was a popular brand of barley wine. However, the availability of barley wine in ‘normal' pubs has decreased in recent years. Nevertheless, many supermarkets still carry Gold Label, giving you the option to use it if you can find it.
To provide a more personal touch, I recall a situation where I had to find a substitute for barley wine while cooking a recipe that called for it. I opted to use an extra stout beer, and it turned out to be a great alternative. The beer's bold flavors added complexity to the dish, and I was pleased with the outcome.
If you can't find barley wine, extra stout beer can serve as a substitute in recipes. Its rich, roasted flavors can provide a similar depth and complexity to dishes. While it may not be an exact match, it can still be a satisfying alternative.