W4: one of 1,022 postcodes stands below a spring high tide

The ground at one of W4's 1,022 postcodes, W4 3UN, is lower than an ordinary spring high tide at London Bridge (3.9 m above Ordnance Datum).

• Ground at eight in ten of its postcodes: between 5.0 m and 9.0 m, measured from Ordnance Datum; the middle one stands at 6.2 m.
• 256 of 1,022 stand lower than the 1953 tide (5.41 m).
• 680 lie in the Environment Agency's Flood Zone 3 from the sea, mapped without defences.
• Mostly in Hounslow; partly in Ealing.