My second purpose built scrambler (after the Dot 250) was a Greeves Challenger Mk1, the 1964 model previous to this one. It had the leading link forks, fibreglass front & rear guards(with moulded in rear no plates). This one looks to have a bigger tank than mine, as well.
The only fault was a very fragile gearbox. A very good bike for it's day.
This looks like a Mk2. The British Motorcycle Owners Club in Mackay has a green Mk3 in outstanding condition which appears and is raced at the Whitsunday Vintage Classic each year. I was lucky enough to ride it a few years ago, great fun!!
Anyone attending in August this year, check it out - it's a beautiful machine.
Mike