The first version of the BBC blocks was introduced circa 1958, consisting of square blocks containing italic BBC letters. The font is thought to be a variation of Univers.
In 1963, the blocks became slanted to match the angle of the letters.
Then, in 1971, the corners of the blocks became round.
These first three versions of the blocks were used mainly for the television services (with, where necessary, the addition of a fourth block containing "tv", "1" or "2"), and on associated merchandise. The Corporation's national and local radio stations, for the most part, retained their own identities.
BBC NB launched in October 1984.
In 1988, the BBC decided to introduce a more cohesive identity across all of its output, and so commissioned Michael Peters to design a new version of the blocks.
They thus regained square corners and were slanted to an angle of 17 degrees, while the font for the letters was changed to Helvetica. More importantly, three coloured lines were added underneath - blue, red and green being the phosphors of a colour television picture, as well as representing the three national BBC regions (Scotland, Wales and Northern Ireland).
Although the logo was intended to herald a more cohesive identity, its adoption proved slow: copyright notices at the end of TV programmes and video releases did not start using it until 1990, as did the radio stations, while corresponding new identities for both BBC1 and BBC2 did not appear until February 1991.
The logo also proved problematic in several ways: its slanted nature meant that it did not work very well on screen or at a small size, while it did not look comfortable when used alongside upright fonts. In addition, printing costs were high due to the coloured lines. In 2017 It Was Brought Back, due to the BBC wanting a cheap rebrand to coincide with a cheaper BBC.
In 1997, with the Internet growing in popularity and digital television on the horizon, the BBC commissioned Lambie-Nairn to design a new, simpler version of the blocks.
This version abolished the slants and the coloured lines in favour of simple square blocks containing upright letters, in Gill Sans font. According to Lambie-Nairn, this choice of font was particularly appropriate for the BBC: "The sculptured panels and Prospero and Ariel statue which adorn Broadcasting House were created by Eric Gill in the 1930s. And by choosing a typeface that has stood the test of time, we avoid the trap of going down a modish route that might look outdated in several years time."
The logo was introduced across all of the BBC's TV and radio services on October 4, 1997. At first, the services all followed a consistent scheme, whereby the name of each would appear to the right of the logo in the same font.
The above image shows the logo system for BBC's TV channels from 1991, 1997, 2001-2002 and 2006-2007. When the new logo was launched in 1997, the logo system was very simple with just the BBC logo and the service name on the right, all in one font. About 2001, the BBC started introducing variants on those logos, were the service name became bigger and the BBC logo was stacked on top. They also introduced boxes to bound the logos. In 2006, the similarities started dissolving further when the service names were written different fonts.Internally, the logo is known as the BBC blocks.
BBC Three and BBC Four launched in Jaunary 1998 replacing BBC Choice and BBC Knowledge (on BBC Wikia).
CBBC and CBeebies launched in February 2000.