Postcode Topographical Race

Someone at work raised this as a possible challenge the other day. To find the shortest route across London that takes in the most postcodes, i.e. the first part of the postcode E1, SW6 etc. May sound simple at first but three of us came up with different ideas for the most profitable routes. I thought an east-west route from Liverpool Street up to Angel and down across to Hyde Park would be a winner. Looking at a postcode map of London doesn’t make it much easier, although it looks like a route across Sw3-Sw6 and north might be a good one.
In judging such a thing, how would you do it?
Pedometers and camera phones – pedometers for the distance, cameraphone to snap street signs showing the postcode and recording the time. It could be a spectator sport if the pictures are blogged (as on this blog). Then the winner could be deduced by dividing the distance by the number of postcodes perambulated. I think there would have to be a creative differential to encourage contestants to be adventurous and really explore the city.
I’d appreciate any comments on this.