E20: one of 225 postcodes stands below a spring high tide

The ground at one of E20's 225 postcodes, E20 1YY, 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 8.5 m and 14 m, measured from Ordnance Datum; the middle one stands at 13 m.
• One of 225 stands lower than the 1953 tide (5.41 m).
• 2 lie in the Environment Agency's Flood Zone 3 from the sea, mapped without defences.
• Mostly in Newham; partly in Hackney.