SW1Y: one of 182 postcodes stands below a spring high tide

The ground at one of SW1Y's 182 postcodes, SW1Y 5ZQ, 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 8.2 m and 17 m, measured from Ordnance Datum; the middle one stands at 12 m.
• One of 182 stands lower than the 1953 tide (5.41 m).
• One lies in the Environment Agency's Flood Zone 3 from the sea, mapped without defences.
• Mostly in Westminster; partly in Wandsworth.