The recipe in Graham Wheelers "Brew Classic European Beers at Home" is just Pale Malt and ~9% Crystal malt.
Given the colour of the finished beer it would have to be a Medium Crystal. My personal choice would be Bairds Heritage Crystal (it a bit darker so somewhere near 8.7% hits the 30 EBC target).
Given the access Wheeler and Protz had/have to breweries I suspect the recipe is pretty much on the money.
The hopping is interesting, about half and half Challenger and Northdown for bittering with Fuggle (about 0.4g/L)in the last 15 minutes, personally I prefer EKG for finishing maybe at around 0.5g/L. Target is 33IBU.
The best yeast I have found is Irish Ale (the old Guinness yeast), I've brewed this beer many times over the years and find the Irish Ale goes closest. Muntons Gold was a good dry yeast, sadly hard to get nowadays.
Keep the Carbonation very low or serve on mixed gas (have used 40/60), the low carbonation makes a big difference to the taste and mouthfeel of the beer.
Bit of a favorite…
Mark
Edit
Sorry it was the Simpsons Heritage Crystal, not Bairds - and no roast or chocolate in sight.
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