

In theory there should be only one high street per locality.

You will have to throw out assumptions like that as soon as you start dealing with addresses in any serious manner.

High Street is a name for the most important shopping street or main thoroughfare in UK convention. I've never been to a place that had 2 high streets and certainly not 2 called High Street. [Many towns in Scotland have a sort of quadrangle of main shopping streets it seems - one is often part cobbled and called Market Street]. If an area/town/village has multiple streets of equal worth then they might be termed North and South street or named for a building like Church Street or such.

In the past having name collisions would simply be a terrible convention, nowadays we have regulations that prevent it from happening with new names (same for housing).

The Scottish village I grew up in had a High Street - but it wasn't the High Street in the sense of "most important shopping street" (or indeed in any other sense). The "most important" street was Church Street - which even had a shop and a church, whereas High Street only had one church. :-)

High Streets can also be overtaken by events. Edinburgh's High Street hasn't been the most important street for anyone other than tourists for a few hundred years.

Use the Royal Mail's 'find an address' tool [1] to look up the following postcodes:

SE20 7QR, SE25 6EP, E13 0AP, E15 2LR, W5 5DB, W3 6LJ, NW10 4SJ, N14 6BW

For a map see [2]. As you can see, plenty there are several roads the Royal Mail considers to be called High Street, London!

[1] http://www.royalmail.com/postcode-finder [2] https://maps.google.co.uk/maps?q=from:SE20+7QR+to:SE25+6EP+t...
