The epic poem Beowulf is probably the best known piece of Anglo-Saxon literature - it's certainly one I was aware of, and had an idea of the shape of the story before we listened to the In Our Time episode about it. However it was unknown until the 19th Century when a single manuscript copy dating from around 1100AD was discovered. The three experts who discussed it on the programme were Laura Ashe (University of Oxford), Clare Lees (King's College London) and Andy Orchard (University of Oxford).
Even tho the surviving version of the poem comes from the 11th or 12 Century, it was probably composed around 750AD. It's sometimes said to be a little earlier: "from the time of Bede" (who died in 735AD). But Orchard pointed out that Bede is known person from a known time so estimates tend to gravitate towards him. The subject of the poem is older still - it's a poem about long ago & far away about history that the listeners were expected to already be aware of. Some of the characters in the poem are real historical personages who lived around the 5th Century AD (however this doesn't include the hero Beowulf). This is a Christian English poem about the listeners' pagan Danish ancestors, written in a time before the Danes were seen as a foreign threat.
There are three sections to the poem. The first tells of the hero Beowulf travelling to another kingdom and fighting the monster Grendel, who has been terrorising the country. Grendel is a misshapen man who fights without a sword and so Beowulf wrestles with him and wins the fight by pulling off the monster's arm. Said arm is then hung up as a trophy when Beowulf returns to the king of the country. The second section tells us about Grendel's mother who comes to avenge her son, as is her legal right. She lives beneath the sea and Beowulf goes to her lair (or hall) to fight her with a sword. The third section of the poem is set 50 years later, when Beowulf is an old man and has become a king in his own right. The story of how he came to be king is told in flashbacks, while the main plot of this section revolves around him fighting a dragon which is terrorising his country. Unlike the first two monsters this is a truely mythological beast instead of fantastical but plausible. Beowulf goes to fight it in its lair, and at first is losing the fight despite his heroic skill. With the help of his men, and using a sword from the dragon's lair, he finally defeats the dragon but dies in his moment of triumph.
The poem has a very non-linear structure, and after its rediscovery 19th Century critics used the repetition as an example of how it was a poor poem. Modern scholarship strongly disagrees with that opinion! The narrative circles around the story with each repetition of an event giving you new details or nuances, or new references to other literature etc. For instance in the first part the poem first tells one about the fight, then Beowulf tells someone about the fight, then Beowulf tells the king of the country Grendel was terrorising and then Beowulf tells his own king. All have differences that tell you more about the event. This isn't the only sort of non-linearity - there are also flashbacks (for instance in the third section as I mentioned above), and asides that tell you how some side-event turned out later. Or who owned a particular sword once the current owner died after the end of this story, and so on.
The poem was written to be heard rather than read. The experts read out sections in the original Anglo-Saxon, with Orchard in particular making it sound vibrant and alive (even if incomprehensible - I didn't get very far the one time I started learning Anglo-Saxon). However it probably wasn't an oral composition, instead it was written down with the intention that it should be read out. It is a very literate poem, with references to other literature of the period and before including classic Latin literature. Orchard pointed out parallels with things like the Aeneid, which the Anglo-Saxons of the 8th Century AD would've known.
It wasn't just a story about heroes and monsters, and tales of derring do. The peom was also about the ending of one era and the beginning of the next. It tells the story of the pagan Beowulf from a Christian perspective, and contains Christian motifs and structural elements. Most obviously the three-part structure which is more of a Christian motif than a pagan one. And the narrative moralises about the actions of the protagonists - a running commentary of "that's how it was then, but we know better now". The pagan culture valued valour & honour, but the Christian one valued non-violence and godliness. The poem reflects that change and the tension between the old ways and the new.
I think the biggest thing this programme told me was how much more there is to Beowulf than I'd realised. I'm pretty sure we have a translation in the house (somewhere!), I should find it and read it sometime :)