Back in 1969 the British government proposed changing over to driving on the right, but this was eventually turned down on the grounds of cost. Nevertheless some motorway junctions were designed and built in the expectation that the legislation would go ahead. You can recognise them by their long deceleration lanes and short acceleration lanes, (the wrong way round for driving on the left), and by a wrongness of the sharper and gentler curves in the slip-roads.
Until 1967, when Sweden changed to driving on the right, there were more miles of road throughout the world where people drove on the left rather than on the right.