Now, 5 years on, Royal Mail has introduced a new postcode to mark 40 Years of Postcodes. So what is the explanation?
Dathlu deugain mlwyddiant y cod post
Celebrating the fortieth anniversary of the postcode
It's not a blunder! The 2009 campaign marked the first steps in the process when the first postcodes were introduced in what was then the NOR area, back in 1959. The process of initial allocation of postcodes to all UK addresses took 15 years and finished when Norwich and Norfolk codes were changed to the NR format in 1974.
So far we've only seen the Welsh version of the new slogan, used on 10 April. More information when we get it!
UPDATE 10.00: Thanks to John Gray for providing the English language version, also from Wales, this time without the 'Delivered by' portion. I've adjusted this to enhance the image.
I have been told by Royal Mail that this postmark was used 10-12 April only. This usually means 'for delivery on' those dates, which would mean 9-11. We'll see what dates other reports bring, to shed light on this.
UPDATE 23 MAY
Intelligent Letter Sorting Machines produce the slogan in this form.