You might not have realised when you posted your clue, Woodinsight, but Jowett has various Hull connections.
One Jupiter was built by local coachbuilder Barnaby Bodybuilders (long gone) but Jowett near its end was actually bought by Blackburn Aircraft Co of Brough, just outside Hull. They made the Blackburn Beverley transport aircraft, amongst others, and more recently the Harrier and Hawk. They are still a big company, part of BAe. Contrary to popular opinion Jowett did not go bankrupt but Blackburns paid off all the company's outstanding debts, but unfortunately wound it up soon after.
The Jowett R4 was used for a time by the MD of both Blackburn Aircraft and Jowett, Eric Turner, who lived in Elloughton, another expensive village in the East Yorkshire countryside near Hull.
Also living in Elloughton from 1960 until his death was long-time Managing Director of Jowett, Arthur Jopling.