BBC Four is a BBC television channel available to digital television viewers in the UK. The part successor (with CBeebies) to BBC Knowledge, the station launched on 2 March 2002.

On 10 September 2005, the channel’s new idents were introduced, based on the theme of “four” and optical illusions, for example a swimming pool where a person on an inflatable ring appears in the bottom left corner, though ripples don’t enter the remaining quarters. Although the image appears as one at the start of the ident by the end it is clearly four separate pics.

BBC Four: Presentation 2005-

BBC Four: Presentation 2005-

A selection of presentation used by BBC Four since September 2005.
BBC Four: Japanese Season

BBC Four: Japanese Season

A selection of BBC Four idents from its Japanese Season, which began on 16 March 2009. My Knees are Laughing Barcode Bald Daughter in a Box Sting Programme Promotion
BBC Four: Abstract art season

BBC Four: Abstract art season

On 8 September 2014, BBC Four introduced a collection of idents coinciding with a season on abstract art.
BBC Four: Pop Art

BBC Four: Pop Art

A special week of programmes about Pop Art.
BBC Four: Idents 2005-

BBC Four: Idents 2005-

On 10 September 2005, new idents were introduced on BBC Four, based on the theme of "four" and optical illusions.