The Innisfallen (V) was actually built as the Leinster in 1968 for the Dublin to Liverpool service.  Following the sale of her near sister, the Cork-based Innisfallen (IV) in January 1980 the Leinster moved to Cork and Rosslare for the Pembroke run, being replaced at Dublin by the Connacht. For her new role she became to fifth named Innisfallen.

The pooling arrangement between Sealink British Ferries and B+I Line saw the closure of the Pembroke service in 1986 and the Innisfallen was subsequently laid up at Dublin. A plan to replace both the Innisfallen and Sealink's St Brendan with a large "jumbo ferry" under a single brand failed to materialise and so the Irish ship found herself sailing between Rosslare and Fishguard as the second ship alongside the St Brendan. The Innisfallen was a poor partner for the Sealink vessel and with continued efforts to secure a larger ferry the 18 year old ship was sold for further service in Greece.

Remarkably, the ship returned to Irish waters in 1990, on charter to Swansea-Cork Ferries as the Ionian Sun. Trading as the Celtic Pride II, the Greek-flagged ship had undergone some changes since her B+I days, including the replacement of her aft lounge with cabins and the extension of her boat deck right aft over the stern. In true Greek style an open air swimming pool was also installed.