The first Rootes Sunbeam was designed by Georges Roesch as Rootes’ flagship. A new 4503cc straight eight engine was designed for the Thirty. It developed 150bhp @ 4500rpm. A four speed gearbox was fitted, without syncromesh on first.
The chassis was based on that of the large Humbers of the period.
It appeared at the Olympia Motor Show in 1936. It was then decided not to put the Thirty into production. The four cars built were all broken up.