The so-called Venerable Bede (c. 673-735) embeds this Anglo-Saxon hymn and the legend of its creation within his Latin text, An Ecclesiastical History of the English People, a book that describes the spread of Christianity in England. The hymn itself was composed in the mid- or late-7th century and so is the earliest surviving Old English poem.
Bede records that Caedmon was an illiterate farmer working for a monastery who at first avoided singing. "Therefore, at feasts, when it was decided to have a good time by taking turns singing, whenever he would see the harp getting close to his place, he got up in the middle of the meal and went home" (25). Modern commentators presume that Caedmon actually "concealed his skill from his fellow workmen and from the monks because he was ashamed of knowing 'vain and idle' songs" (24). The generic scene described does sound like a mead-hall revel. According the the legend, Caedmon had a mystical experience in his cattle shed in which he was given a calling to sing: first, about Creation.
The hymn well represents Old English poetry, with its lines of four stresses and a medial caesura, with its two or three alliterations per line, with the stacking up of epithets (God is guardian, measurer, lord, creator, master). As always in Anglo-Saxon culture, the Old Testament God works better than the New. And the reference to "heaven as a roof" may evoke the security of identity with an implicit comparison to the enclosure of the mead-hall. Praising God's creative ability even seems to function somewhat as a boast.
Just like Hildegard of Bingen because of her visions manifested in the arts, Caedmon must appear before "learned men so that they might judge what the nature of that vision was and where it came from" (26). The indications suggest that since Caedmon accepted commissions, or topics, his gift wasn't spontaneous divine inspiration. Ultimately he became a brother in a monastery, known for his religious songs. "Whatever he learned of holy Scripture with the aid of interpreters, he quickly turned into the sweetest and most moving poetry in his own language" (25).
Bede. From An Ecclesiastical History of the English People. The Norton Anthology of English Literature, Volume I. 8th ed. NY: W.W. Norton & Co., 2006. 24-27.