US subscriber - hardly anyone seems to know what it is (sadly I guessed right)
The CZ tee and Suzuki tape are red herrings - it's a JSD250. John Surtees (yes, that one) built these in the early '60s using the famous Reynolds 531 cycle tubing and Earles forks ; the engine's a "Hailwood" Ducati 250 Desmo twin cam parallel twin. Seems funny to think of someone making a frame to improve a Ducati's handling these days, but 50 years ago things were very different in Bologna.
The story goes (and Ducati's own conflicting webpages have been taken down) Stan Hailwood got Taglioni to design Mike a 250 based on the 125 Desmo twin (featured in Benzina #3)- and while he was at it, Dr T built Ken Kavanagh a 350, which also finished up in the Hailwood's garage.
But, although powerful enough the 250 especially was just too heavy and, Mike said, "handled like a 5-bar gate." Underdeveloped and unreliable, Hailwood hardly used the bikes. In 1961 they were sold to John Surtees, who built the "John Surtees Ducati" for brother Norman (and others) to race.
These's more love for Ducati's racing twins here