Obviously, the records relevant for any ancestors of Irish descent born in the UK are UK records, and the research techniques are the same as those for researching UK ancestors. Only when research reaches the individual who migrated from Ireland to the UK is it necessary to look at British records from a particularly Irish point of view. And there are then two separate but equally challenging questions to be answered:

Any researcher working on records more than 60 or 70 years old needs to keep in mind the possibility of various surname spellings. For Irish ancestors these spellings are a certainty. Before the 20th century the 'O' and 'Mc' prefixes were treated by record-keepers as entirely optional. McCarthy may appear as Carthy, Carty, Cartie; O'Brien will usually be Brien (or Brian, or Bryan, or Bryen ...). In addition, it has to be kept in mind that the vast majority of Irish immigrants were illiterate or semi-literate, very often spoke Irish as their first language and invariably had more pressing concerns than the precise spelling of their surname. From the 17th century onwards, Irish surnames were translated, pseudo-translated, transcribed phonetically and transposed to their nearest English equivalent. So Mac Gabhainn, from gabhann, meaning 'blacksmith', became Smith, Gowan or McGowan; OhEarrachtáin became Harrington; Mac an Dheanaigh, from deánach, meaning 'dean' became McAnany (or McEnany, or McEneny, or McAneany ...) phonetically, or Deane by translation, or even Bird, because of a spurious resemblance to eán, the Irish for bird. Given this, it is not at all uncommon for members of the same Irish family to appear in the same record with different surnames.

The vast majority of Irish records are location-specific, which means that in order to use them it is necessary to know a place of origin in Ireland. Realistically, the county of origin is the minimum you need and this can be quite difficult to discover.

All these record the place of birth but, unfortunately for most Irish people this is simply given as 'Ireland', although in some cases the county of birth may be recorded.

Tip: Migrants from the same areas tended to stick together. Look at the returns for Irish households in the same or neighbouring streets - if any record a county of origin in Ireland, the likelihood is that most, if not all, of the Irish immigrants in the area came from that county.

Civil records are available from 1837 for England and Wales and 1855 for Scotland. Unfortunately, the information recorded does not include a place of origin.

Tip: It is possible to draw conclusions about the date of migration from negative information - a birth or marriage that is not recorded when or where you expect it to be may in fact have taken place in Ireland.

Roman Catholic records may sometimes record the parish of origin of the parents in the case of a baptism. Even where a marriage has already been uncovered in civil records, it can be worthwhile checking the church record. As well as a place of origin in Ireland, the church record may also record the maiden names of the mothers of the two people marrying.

Virtually all wills probated in Ireland were destroyed in 1922. However, where any of the property covered by the will was located in England or Wales there is probably at least a copy in a UK repository and before 1858 this will be the Prerogative Court of Canterbury. From 1858 to 1922, summary details will be found in the National Probate Calendar.

Tip: The will of someone who migrated from Ireland to Britain may very well contain information relating to family still in Ireland, inevitably with good information on the place of origin.

Almost anything with a name on it can provide genealogical evidence. Old letters can provide a straightforward address, but even without this any names of prominent individuals mentioned in the text - priests, magistrates, politicians - may give a clue as to the place of origin. Even the postmark on the letter may be useful. Copies of old Irish newspapers (invariably local) may give a pointer. Photographers' names, usually printed on the back of old photographs, might allow the identification of the relevant area from local Irish directories. Even first names can sometimes give a pointer in the right direction.

In addition to British records, there are further original Irish records in the UK, including service records, as well as copies of Irish records, that you can consult here before you need to start your researches in Ireland.