George Birkbeck Norman Hill,
The Life of Sir Rowland Hill and the History of Penny Postage…
“ They can be cleared at all hours of the night, when receiving-houses and sub-post offices are closed; a convenience especially valuable in London, in reference to the morning mails. Their superiority in respect of economy is obvious; and this valuable quality so facilitates their multiplication that in London, by the close of the period, there was scarcely a house but had a posting-place within a furlong. ”
