In 1841 the GWR opened its first main line between London and Bristol. It was engineered by Isambard Kingdom Brunel and the track was on the broad gauge, in contrast to most of the railways already in existence in Great Britain. The broad gauge would, Brunel argued, give greater stability to trains running at speed. In 1844 a branch line from Didcot to Oxford was opened, preparatory to extending the GWR system into the West Midlands. It too was designed by Brunel, and used the broad gauge.