Mizter T wrote:

No - the official Royal Mail requirement to include postal counties
continued past the creation of Greater London. I'll try and find the
date when the requirement was dropped.

It was in 1996.

Most English postal counties *did* change in the local government
reorganisations of the 1960s & 1970s, with the following exceptions:

* London was not changed due to stretched finances in the 1960s.
* Middlesex continued to be used except for Potters Bar which was move to
Hertfordshire.
* Herefordshire and Worcestershire were kept separate.
* Humberside was split into North Humberside and South Humberside.
* Greater Manchester was not introduced in the 1970s because of potential
confusion with the "Manchester" postal town.

The E4 postcode is part of the London postal district. "Greater
London" has absolutely *no meaning* whatsoever in a postal address
sense - cast-iron fact.

Not totally. Since 1996 the county field has been optional and people have
been able to use what they like, and "Greater London" (or even just
"London") is a valid county entry.

The Church of England's Diocese of London only covers part of Greater
London (and includes at least one bit outside of Greater London,
Spelthorne),

That's because the Diocese is named after the City of London, which is the
bishop's seat, not the whole metropolis.