Complex sentence: The One Network was formed following the merger of GWR Group and Capital Radio in 2005, merging GWR's "Mix Network" with Capital's "Capital FM Network" and was relaunched in September 2007.
Split into simpler sentences: The One Network was formed following the merger of GWR Group and Capital Radio in 2005. It merged GWR's "Mix Network" with Capital's "Capital FM Network" and was relaunched in September 2007.