1938 Vauxhall Wyvern H-series Caleche. Bodied by Holden in Australia, and based on what was known on the UK as the Vauxhall 10/4.
I don't think the Wyvern designation was used in the UK until the post-war L-Series, but I could be wrong. This car was the subject of an article in Classic and Sportscar within the last couple of years, which is how I solved it so fast.