Complex sentence: However, speed restrictions outside of built-up areas were only introduced in Britain in 1965, so in 1949, neither the car nor motorbike would have been subject to any speed restrictions for most of the journey.
Split into simpler sentences: However, speed restrictions outside of built-up areas were only introduced in Britain in 1965. So in 1949 neither the car nor motorbike would have been subject to any speed restrictions for most of the journey.