RegEx for matching UK Postcodes

Question

I\'m after a regex that will validate a full complex UK postcode only within an input string. All of the uncommon postcode forms must be covered as well as the usual. For in

Answer 1

An old post but still pretty high in google results so thought I'd update. This Oct 14 doc defines the UK postcode regular expression as:

^([Gg][Ii][Rr] 0[Aa]{2})|((([A-Za-z][0-9]{1,2})|(([A-Za-z][A-Ha-hJ-Yj-y][0-9]{1,2})|(([**AZ**a-z][0-9][A-Za-z])|([A-Za-z][A-Ha-hJ-Yj-y][0-9]?[A-Za-z])))) [0-9][A-Za-z]{2})$

from:

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/359448/4__Bulk_Data_Transfer_-_additional_validation_valid.pdf

The document also explains the logic behind it. However, it has an error (bolded) and also allows lower case, which although legal is not usual, so amended version:

^(GIR 0AA)|((([A-Z][0-9]{1,2})|(([A-Z][A-HJ-Y][0-9]{1,2})|(([A-Z][0-9][A-Z])|([A-Z][A-HJ-Y][0-9]?[A-Z])))) [0-9][A-Z]{2})$

This works with new London postcodes (e.g. W1D 5LH) that previous versions did not.