EC3N: one of 81 postcodes stands below a spring high tide

The ground at one of EC3N's 81 postcodes, EC3N 4DT, 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 12 m and 16 m, measured from Ordnance Datum; the middle one stands at 14 m.
• One of 81 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 City of London; partly in Tower Hamlets.