This name is a synonym of Centranthus ruber subsp. sibthorpii (Heldr. & Sart. ex Boiss.) Hayek.
The record derives from WCSP (in review)
(data supplied on 2012-03-23)
which reports it as a synonym with original publication details: Bot. J. Linn. Soc. 71: 221 1975 publ. 1976.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:892269-1.
This name was in version 1 of The Plant List, record kew-2709050.