Yes there is a tunnel (I walked past tonight) - it runs under the two gables that you can see in the Bing imagery.  The hedge in the Bing imagery to the west of the west gable no longer exists.  
Also, if you look at the houses on the east side of Juniper Close, you can see 3 similar features.  Those are also tunnels but appear to be only used to access back gardens.  You can see from the shadows on the imagery how the fences to the east of the houses stop before the house walls - that's so people can get from the shared building passage to each garden.