On 20 April 1964, the launch of the channel was delayed by an infamous power failure in Central London the day before due to fire.
One day after, it launched.
On 1 July 1967, the first official colour channel in the UK launched on UHF and with it came a brand new ident.
1975–1978 (secondary), 1979–1986 (primary)
In December 1975, the BBC introduced the two curved lines that form the number '2' as "The Tinsel 2", then the logo came back in December 1978, but it did not become the official logo for BBC2 until April 1979. The logo was phased out on 31 March 1986.
BBC Two (first era)
Visa (digitised as Avia)
The channel wanted to aim programming that was more high brow and sophisticated. As a result, they wanted the new logo to reflect this. The BBC commissioned Alan Jeapes, who was responsible for the title sequence for BBC1's hit soap EastEnders the year before, to create the new look.
Based on Gill Sans ("2") Helvetica Neue (BBC logo)
After 5 and a half years of the dull and worthy identity in 1986, as part of an extensive rebrand to cast off BBC2's "highbrow" tone. Lambie-Nairn launched a brand new set of idents, featuring a numeral '2', which originally lasted for 10 and a half years until they were replaced in 2001. This extensive rebrand occurred on 16 February 1991.
Throughout November 2001, the logo was slightly modified, being stacked and placed inside a purple box. The idents were changed for the first time in 10 and a half years; the "2" symbol stayed the same, but it was given a pair of arms and a "personality". The BBC added to the roster of 4 idents over the years.
A new logo was introduced on 18 February 2007, with the typography on the word "TWO" being changed from the Gill Sans typeface to the Avenir typeface, and the box's colour changing violet to teal. The blade "2" has been slightly altered for this look.
From 2018 this is now a secondary logo.
The boxless variant of the 2007 BBC Two logo has been used in the promos since 2012 and on the revived 1991 ident package in Northern Ireland from 1 January 2015. On 27 September 2018, BBC Two launched a new look, uses the boxless 2007 logo and ditched its famous "2" icon that has been in use since 1991. The box logo from 2007 is currently used as a primary logo and the "2" symbol resembles a curved wave.
Used from 16 February 1991 to 18 February 2007. From 2001 to 2007, the 1991 2's replaced the white 2, and the few idents had robotic arms. To celebrate its 50th birthday in 2014, BBC Two brought back many old idents, including the 1991-97 and 1997-2001 set of idents featuring the "2". In 2015, the 1991-2001 set of idents and stings were brought back on a more permanent basis.