HA0: 16 m clear of the highest tide in the London Bridge ledgers

The lowest postcode in HA0, HA0 1JG, stands 16 m above the highest tide in the London Bridge ledgers (5.41 m, 1 February 1953). The highest, HA0 2QQ, stands 74 m above it.
- Ground at eight in ten of its postcodes: between 28 m and 58 m, measured from Ordnance Datum; the middle one stands at 41 m.
- None lies in the Environment Agency's Flood Zone 3 from the sea.
- Mostly in Brent; partly in Ealing.