The groups , who were big names in the UK pop music scene in the late 1990s and early 2000s , reunited Cause_to_amalgamate for the ITV2 reality-documentary series `` The Big Reunion '' ( apart from Blue , who had already been reunited Cause_to_amalgamate since 2011 ) , a show Social_event which follows Motion them meeting Social_event again for the first time in a decade and rehearsing ahead of their comeback performance .