There does not appear to be any info on this bike online, despite mention in the article of units being offered for sale. Were any actually sold?
Fortunately, racer Peter Crew, who was involved with this project saw this post and sent in some more details on the story.
Thank you Peter!
Regarding the 250cc Merlin story, the story begins with Frank Higley who thought it was a good idea to contact Chris Merlin, a clever and capable engineer who raced karts. Chris used the standard Villiers engine but cast his own crankcase half to convert the engine to disc valve, and using this engine in 200cc form was unbeatable and won the 200cc British Kart championship.
Frank asked Chris to convert the engine to 250cc with the intention of putting it into a bike race frame, so they fitted a 250 Greeves Silverstone barrel with the inlet blanked off and the offset exhaust. Frank commissioned Denis Evans to build the frame and complete bike, this is the bike in your photo. Subsequent developments were a proper barrel with a center exhaust and no inlet and a copy of the Silverstone cylinder head. The bike was tested by Bruce Main Smith from the Motorcycle magazine and I have a copy of the racer test, but it seems despite some capable riders the bike didn’t achieve much. I have been friends with Denis for over 50 years and he lives near me so I knew of the bike. Denis told me that he built a 350cc version, his own engine and chassis and wished he could find it again.
Jump forward several years and in 1983 I decided I wanted to get back into racing again, and found a 250 Merlin engine for sale in Scotland, I contacted Denis and he was dead keen and said buy it, it was only £50! Denis has an unfinished chassis in the workshop and so the Merlin was reborn. It was a horror story getting it competitive and reliable but once we changed the Villiers parts for Jap parts it was semi reliable but very fast. From 1984 to 1998 I won over 100 races on it, club level and National, and as a consequence Classic Racer magazine did an article on the bike and Denis, and this led to an amazing coincidence where I got a phone call from someone who said that he had been reading about the bike and that his brother has a barn full of them. I got Denis and we travelled to the location (not 12 miles from us) and there behold was the original Merlin plus his 350 together with many other bikes that belonged to Frank Higley. So that is how we got them back, Denis is over 90 years of age now and still reminisces about these bikes, we had fun.