Royal Mail
It was/is a symbol of prestige that the carrier had been specially selected to carry His/Her Majesty's Mail.
It followed then, that such carrier was perceived to be loyal, dedicated, safe and reliable - Her Maj said so, OK?
Similarly, one will find products and services wearing the "By Royal Appointment" seal in their advertising.
An example would be Alfred Dunhill & Company - Purveyors of fine cancer-sticks to the Royal Household.
Not sure that particular arrangement would still exist, though.
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Last edited by Stanwell; 26th Jan 2015 at 22:23.