These cover parts of southern Greater London and north-east Surrey.

Croydon was the second town, after Norwich, to have experimental postcodes, introduced in 1966.

This trialled the postcode area CRO (letter 'O'), while Norwich used NOR for its equivalent.

It was decided that the outward (first) part of a postcode should be alphanumerical, so CRO became CR0 (with a zero) and NOR became NR1.

[3] The approximate coverage of the postcode districts: Delivery offices are located at Croydon, South Croydon, Caterham, Mitcham, Coulsdon, Thornton Heath and Purley.