For many years the P&O House Flag flew aboard ferries calling at the most northern ports of the UK. The time-line below charts P&O's involvement in the northern fleet.

1856	Locally-owned steamer service starts from Stromness to Scrabster.
1882	Service taken over by North of Scotland, Orkney and Shetland Steam Navigation Company, using the St Olaf.
1883	St Rognvald joins the fleet, and is the first ship to bear the name.
1887	The first ship to bear the name St Sunniva for their Norwegian cruise programme.
1892	The first ship to bear the name St Ola is built at a cost of £11,000 and operated for 57 years.
1951	North of Scotland, Orkney and Shetland Steam Navigation Company take delivery of the new 750 ton St Ola.
1971	P&O became the parent company of the North of Scotland, Orkney and Shetland Shipping Company. P&O also announched the building of a new £1.4 million ferry.
1975	The third ship to bear the name of St Ola enters service replacing the previous St Ola and is the first ro-ro ferry to serve Orkney.
1977	The St Clair becomes the first of the new generation of ships to be introduced for Shetland.
1987	P&O mark their 150th anniversary with the new St Sunniva linking Orkney with Aberdeen and Shetland. Two previous north ships had carried the name, one ran aground off Shetland and the other was sunk during World War Two.
1989	In January, the company changes its name to P&O Scottish Ferries.
1991	P&O spend £9 million on buying the former Baltic ferry Eckeroe which would become the last St Ola.
2002	On October 1, P&O Scottish Ferries bow out as a new operator Northlink Ferries enter the scene.