It was broadcast between March 12 and April 16, 1978, as a six-episode series.

A six-episode series concluded in the UK on 19 April 2009.

Two six-episode series were made, along with a pair of 45-minute Christmas specials.

It was then followed by a six-episode series that was commissioned on E4 and broadcasting began on 7 October 2010.

An unaired pilot episode was made in 1982, and a six-episode series was commissioned.

A second six-episode series began airing in the UK on Sunday 7 October 2012.

It ran for one six-episode series from September to November 1970.

The haunted character of Callan caught the public's imagination to such an extent that a six-episode series was commissioned, later in the same year.

The six-episode series premiered on December 12, 2009.

Slammed by the critics, it aired in just one six-episode series.