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If there is no pavement, keep to the right-hand side of the road so that you can see oncoming traffic.
(http://www.highwaycodeuk.co.uk/rules-for-pedestrians---gener...)
For the Americans, pavement in British English means sidewalk :)
After learning this (in school road safety lessons I think?) in general I always assumed you should walk on the right as a pedestrian for consistency (even though the highway code doesn't contain any rules for sidewalks) but it's not universally observed, particularly in London where there are so many foreign tourists.