After the introduction of the uniform penny post in the United Kingdom in 1840, postal volumes grew rapidly and were an increasingly important part of goods traffic between Great Britain and Ireland. In 1849, the Post Office invited tenders for a mail contract from Holyhead to Kingstown (now Dún Laoghaire) which was ultimately awarded to the City of Dublin Steam Packet Company (CoDSPCo) which began its service in 1850. Over the following years the London and North Western Railway Company (LNWR) became the dominant railway company and began operating its own ships on the Irish Sea. This led to friction with the CoDSPCo.
In 1882, new tenders were sought for the rail and sea elements of the mail contract. The LNWR were the only contender for the rail journey from London to Holyhead and put in a price for a combined rail and sea operation which was initially accepted by the Treasury. This caused dismay in Ireland and Irish MPs lobbied the Government to seek new tenders. This was done and the CoDSPCo’s offer for the sea operation was accepted. In 1895, after lobbying by both sides, the contract was renewed until 1917.
As part of the deal, CoDSPCo ordered four new mail steamers named for the four Irish provinces, RMSs Connaught, Leinster, Munster and Ulster. Around 650 passengers could be carried at a maximum speed of 23 knots.
In response, LNWR brought four new express steamers for their Holyhead to Dublin North Wall service and two slightly smaller ones for their Holyhead to Greenore (Carlingford Lough) service, which they planned to develop. Around 650 passengers could be carried at a maximum speed of around 21 knots. On the two services operating between Holyhead, Dublin and Kingstown, the plan was for two ships to be in operation. Each ship made a return trip every 24 hours (one ship doing night and one ship day crossings) and working to a timetable. The third ship would be on standby to cover any problems. The fourth ship would be undergoing maintenance or inspection.
In 1908, LNWR moved their express passenger service from Dublin North Wall to Kingstown after a dispute over port charges. At the outbreak of war in August 1914, the Admiralty immediately requisitioned the four LNWR express steamers with one CoDSPCo mail steamer being added in 1915. The LNWR decided to maintain their express service by using the two Greenore ships Rathmore and Greenore, and moving back to Dublin port. The company kept an older ship on standby.
When peace came, tenders were sought for a new contract which was won by the LNWR on price. This time the new Irish MPs had no time to spare for lobbying on the mail contract on behalf of the CoDSPCo. Elected in the UK General Election of December 1918, the overriding topic was Irish independence.