SW1X: 2 of 400 postcodes stand below a spring high tide

The ground at 2 of SW1X's 400 postcodes (under 1%) 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 5.7 m and 9.5 m, measured from Ordnance Datum; the middle one stands at 7.2 m.
• 19 of 400 stand 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 Westminster; partly in Kensington and Chelsea.