Located on Windsor High Street next to the Guild Hall is a green hexagonal Penfold post box.

This broke the standard pattern and so in 1866 the Post Office again produced a standard letter box. This time the box was designed by J W Penfold and came in three sizes. Problems were encountered with some of the early designs however and modifications were made, such as the inclusion of downward-pointing shoots to help prevent letters being caught up in the cap of the box. The ‘Penfold’ letter box while not particularly a success operationally was very popular with many people.

As a standard box however it was not to survive. In 1879 a further standard box was produced. This time more of the earlier lessons were taken on board. The new standard box at last resembled the letter box that is today the iconic image of Britain – cylindrical with round cap and horizontal aperture under a protruding cap with front opening door and black painted base.

The Postal Museum Website explains how the Pillar Boxes went from red to green and back again.