Container Enterprise & Container Venturer
Built in 1958 for service between Heysham and Belfast the Container Enterprise and the Container Venturer were the first British Railways ships specially designed for carrying containers.
As far as I know they were never in service at Holyhead, but were regular visitors to the port for the attention of the marine workshops. In 1971 the "Enterprise" was moved to the Fishguard - Waterford service and shortly before its closure in 1976 the "Venturer" also saw time on this exposed crossing. The ships were then sold by BR.
In 2004 the Container Venturer was still in service under Cambodian ownership as the Sunshine One.