Are you sure that it was #Wikipedia? Because this is the sort of thing that has endless modern GitHub and #StackExchange posts, and a claim that there was an official government regular expression at one point in the past.
https://stackoverflow.com/a/51885364/340790
https://github.com/stemount/gov-uk-official-postcode-regex-helper/blob/master/README.md
Whereas Wikipedia has had the British Standard mentioned for almost 20 years at this point, not 15.
Before then it had a haphazard half-arsed list of #RegularExpressions, where every so often someone had come along and appended text saying that "well, actually, the aforegiven does not work; *this* is the *more complete* regular expression".
https://en.wikipedia.org/wiki/Special:Diff/23157377
It had grown 4 times in that way with a succession of invented regular expressions, each one described as "more complete" than the last, by the time someone came along with the #BS7666 one in 2006 and switched from Perl syntax to standard POSIX syntax.
https://en.wikipedia.org/wiki/Special:Diff/89001370
The "Well, actually"s were gradually approaching it.
JdeBP
Mark Tyndall