|30 April 2010 - 1 December 2012|
The channel was the high definition simulcast of S4C. The name "Clirlun" reportedly is Welsh for "Clear View", and was the winner of a competition devised by S4C in 2010 to create a Welsh name for high definition.
According to a press release issued at the time of launch, it had been originally foreseen that all content for S4C would be offered in high definition by the end of 2012.
The channel was only available to a relatively small group of viewers with Freeview HD receivers to begin with, going on air at the end of April 2010 across South Wales and parts of Mid and West Wales. Clirlun and the rest of Freeview HD was added belatedly in North Wales and Pembrokeshire, as part of a scheme to "retrofit" transmitters that had gone through digital switchover prior to Freeview HD services launching. The channel never launched on other digital platforms.
Earlier this year, the channel complained about "English transmitters" interfering with the Clirlun signal in North East Wales. By July, S4C had announced the closure of the Clirlun HD channel, with the broadcaster bagging losses of £6million ahead of a transfer of funding from the BBC licence fee.
In October, Ofcom confirmed that Channel 4 would be able to take the capacity on the Freeview HD multiplex in Wales to launch its Channel 4 HD service to viewers in the Principality. Originally indicated as taking place at midnight on the 1st December, the closure of Clirlun has now been altered to 23:59 on the 1st - so practically midnight on the 2nd December.
S4C's standard definition service will continue on Freeview channel 4 in Wales, with Channel 4 (standard definition) on 8.