Terry Joslin

The Douglas 600 OB was a late 1920s British flat-twin, developed from Douglas’s horizontally opposed engine layout. Its 596cc side-valve twin produced around 25 bhp, favouring smooth torque delivery over peak output.

With a low centre of gravity and stable chassis, it handled well by period standards, making it effective on UK roads and in reliability trials. It reflects Douglas’s focus on balance, durability and practical performance.