I propose to take Questions Nos. 899 and 901 together.
A common travel area exists between Ireland and Britain which means that there is no formal passport requirement for Irish citizens (including, of course, Irish citizens born in the United States and carrying Irish passports) travelling between the two countries. An immigration officer may, however, ask a passenger for evidence in support of a claim that he or she is an Irish citizen. Supporting documents for this purpose apart from a valid passport could include, a valid driver's licence, a valid International Student card with photograph, a valid bus pass with photograph or valid work identification with photograph.