Walking issue

Spending couple of days in London this week i noticed a trend. Despite the fact that cars in UK drive on the wrong side, people, by and large, still tend to walk on the right side of sidewalk. It was especially noticable on long stretches without any possibility to turn, like "Millenium" bridge (but this one doesn't really serve as a proof since it's touristy area), but also on Oxford street and other busy sidewalks.

I wonder if it's something inherent to people, or maybe there's some very easy explanation, like the fact that most people carry their bag on right shoulder, and walking on the right keeps the bag from hitting those, who're walking in the opposite direction.