It was created in 1797 for Francis Mathew, 1st Viscount Landaff,[1] who had previously represented County Tipperary in the Irish House of Commons.
[4] Thomastown Castle was the childhood home of Father Theobald Mathew, "The Apostle of Temperance".
[5][6] The Earls Landaff used the invented courtesy title Viscount Mathew for the heir apparent.
Despite their territorial designations and the fact that they were in the Peerage of Ireland, the titles all referred to the place in Glamorgan now spelt Llandaff.
The seat of the Mathew family was Thomastown Castle, County Tipperary long abandoned.