They are an invaluable (if sometimes inconsistent) account of the Portuguese discoveries under Prince Henry the Navigator, and one of the principal sources upon which historians of the era have drawn.

Probably a native of Lagos, Portugal, Diogo Gomes began as page in the household of Prince Henry the Navigator and subsequently rose to the rank of cavaleiro (knight) by 1440.

[1] He was named a royal clerk (escrivão da carreagem real) on 12 June 1451, and went on in the service of both Prince Henry and the Portuguese crown.

However, modern historians find this improbable; Russell notes that, at the time, 'Indian' was commonly used as a moniker for an Ethiopian, and the furthest hope that Henry nurtured was of reaching the lands of Prester John.

Gomes credits himself as the first Portuguese captain to interact peacefully with the natives in this region (all prior expeditions had been fended off or fallen in hostilities on the Senegambian coast, although Alvise Cadamosto had also sailed successfully that same year).

Although the region was primarily Muslim, Gomes seems to have won over at least one important chief named Numimansa, with his court, to Christianity and Portuguese allegiance.

Gomes speaks, with some resentment, of how Antonio de Noli managed to reach Lisbon before him and secured the captaincy of Santiago island from the king before his arrival.

Already in advanced age, Diogo Gomes orally dictated his memoirs to the German cartographer Martin Behaim during the latter's sojourn in Portugal.

Historian Peter Russell tentatively dates the interview around 1499, as the account refers to the death of António de Noli, which occurred around that time.

Historians generally treat Diogo Gomes's account with caution - his penchant for self-promotion, his advanced age, his attempt to recollect events more than two decades past, misunderstandings by Behaim's interpreter, the haste of the transcription (the Latin is quite poor, suggesting it was hurriedly written) and possibly even some supplementary massaging of the material by editor Valentim Fernandes or Behaim, have conspired to make it an imperfect document, with numerous errors and inconsistencies.

Gomes notes Henry sent out his caravels to search for new lands (ad quaerendas terras) from his wish to know the more distant parts of the western ocean, and in the hope of finding islands or terra firma beyond the limits laid down by Ptolemy (ultra descriptionem Tolomei); on the other hand, his information as to the native trade from Tunis to Timbuktu and the Gambia helped to inspire his persistent exploration of the West African coast to seek those lands by way of the sea.