According to Ryanair’s terms and conditions on their site it specifically states that “A driving license is not accepted as a travel document on international flights.” Flights between the UK and Ireland are obviously international as they are two different countries and this will not be a domestic flight.
Full details of the requirements can be found here:
International travel requires a valid passport, or you could also use an Irish Passport Card.
Whilst Ireland and UK are in the Common Travel Area and you do not need a passport to enter either country if you travel from the other, that is an immigration issue. This is just part of the requirements for travel – in addition you may have specific requirements by the airline you travel with and you will need to meet these in addition to any immigration requirements.
This issue has been in the news in the past and has highlighted that Ryanair does have its own requirement for all travellers between Ireland and the UK to have valid passports and it has even gone as high as the Irish Government, which refused to issue a bill to ensure that the requirement for a valid passport is waived.
So as far as it stands I am afraid you will not have a valid argument to hold Ryanair liable as their terms of carriage were clearly stated on their website and by purchasing tickets you would have agreed to them.
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