Continued with work on the cylinder head. Managed to get one of the exhaust flange bolts out but the other will not budge. Drilled out the two sheared off bolts in the cylinder head and tapped them out to 5/16″ BSW. Managed to shear off the water drain tap when trying to remove it from the crankcase 😦 On a more postive note, I had a reply from Mr. Lister, David Edgington. He was able to tell me that this engine was supplied new to a Mr William Cook, an agricultural dealer from Peterborough, Cambridgeshire, on the 18th August 1942.