If you are planning on travelling between London and Ireland by train and ferry, you may well need to take this Virgin train between London Euston and Holyhead. New trains on this route have recently been introduced by Virgin. They are clean and comfortable, with a bar serving snacks and drinks. Seats have power sockets, and wireless internet access is available (for an additional fee).
The journey takes around 3hrs and 40mins, depending on the day of travel. There are around five services each day.
If you are travelling to/from Holyhead ferry terminal, you will find the train station next to the ferry terminal, so no other interchange is required. The ferry terminal can be found at the end of Platform 2. If you are hoping to catch a ferry to Ireland after arriving by train, make sure you allow for the check-in time (generally around 45mins).