In the ‘ Testimonium ’ prefixed to the ‘ Annals of the Four Masters ’, and signed by four Franciscan friars, the chief of whom was Bernardine O'Clery, guardian of the convent of Donegal in 1636, there is an enumeration of the principal sources from which the latter portion of the annals was compiled. The last-mentioned of these sources was the ‘ Book of Lughaidh Ó Clérigh ’, which the friars say covered the period 1586–1602. This book, we are to infer from the notice, was written in the form of annals. The other sources referred to are described in such a way as to show that they too were written in annalistic form.
The ‘ Book of Lughaidh Ó Clérigh ’, unlike some others utilized on the same occasion, has come down to us. It is now known as the ‘ Life of Hugh Roe O'Donnell ’, though that title does not appear in the sole authoritative manuscript. Indeed, the form of annals is preserved throughout, though it is not emphasized in the edition published by Denis Murphy in 1893.