Today, most Britons live at relatively high population density in an urban environment and don’t move around that much on foot from where they live or work. A mile can actually cover very different neighbourhoods or include hotspots that may have little bearing on your immediate environment. That’s why we realised that we needed to add in two new radius levels for crime for all 1.7 million postcodes (except Scotland). As you’ll see here in this example postcode;
http://www.ukcrimestats.com/Postcode/se12nb
there is a dropdown box for 0.5 and 0.25 miles as well as the default of 1 mile.