This looks a lot like the 1955 Sun Wasp Champion du Monde on Classic Lightweights. We know it's no older than 1952 as the World Pursuit Championship decal is in reference to Sydney Patterson's win for Sun that year. He repeated in 1953. Reportedly, TI bought Sun in 1958 and from 1964 the frames were manufactured by Carlton and carry a Worksop identifier, so it shouldn't be any newer than that.

There should be a double letter prefix for that serial number. Format is reportedly yLxxx, where y is a letter designating the year and T reportedly indicates 1952/1953. L indicates the lightweight division. xxx is the frame number for the year.

This one looks like it has been rebuilt. The rear derailleur looks like a mid-1970s Huret. The brakes are probably replacements too. At least it still has the original badged stem. Those are reportedly worth a lot of money. Some Sun models used Reynolds 531, so I'd be measuring the seat post diameter to determine the tubing.

See Restoring an original classic: Sun Wasp 'Champion du Monde' 1955