The Old English poem known as 'The Battle of Maldon' survived into modern times in a single, incomplete, manuscript - both the beginning and end of the poem were missing.
It was common Anglo-Saxon practice to form a quire from four sheets of parchment - folded to make eight leaves. It seems likely that the poem was written on one such quire, and that, before the seventeenth century, the outer sheet (i.e. the first and last leaves) became detached and lost. It has been estimated (D.G. Scragg 'The Battle of Maldon') that fewer than sixty lines have been lost from the beginning of the poem, with slightly more from the end.
The manuscript found its way into the collection of Sir Robert Bruce Cotton (1571-1631).
The poem, with a selection of other items, was bound into a volume: Cotton Otho A xii.   Cotton used a unique cataloguing system. Otho A xii was the twelfth book on the top shelf of a bookcase, which was topped by a bust of the Roman emperor Otho.
On Saturday 23rd October 1731, the library housing the Cottonian collection was devastated by fire. The sole surviving manuscript of 'Beowulf' was damaged in the fire, but among the many works totally destroyed was 'The Battle of Maldon'. Fortunately, a transcript of the poem had previously been made, by one John Elphinston. This transcript had been used, by historian Thomas Hearne, to produce a printed version in 1726. In the early 1930s, Elphinston's transcript was discovered among papers belonging to Hearne. On linguistic grounds, D.G. Scragg suggests that the poem was composed in the late-10th or early-11th century.
The poem, as it now exists, begins with Byrhtnoth deploying his troops for battle. He orders them to dismount and chase their horses clear of the site. He rides amongst them, giving instruction and encouragement, before himself dismounting amongst his most loyal retainers.
The battle of Maldon is mentioned in the 'Vita Sancti Oswaldi' (Life of St.Oswald), written c.1000 (usually attributed to Byrhtferth of Ramsey). Byrhtnoth is said to have been "tall of stature standing above the rest". Reference is made to "the swan-white hair of his head" and "the weakness of his body". Indeed, the evidence suggests that Byrhtnoth (who became ealdorman of Essex in 956) was over sixty years old at the time of the battle.
Byrhtnoth's men are facing a Viking army across a tidal river - the Pante (now the Blackwater). A Viking spokesman (none of the Vikings are named) calls across the water. He demands tribute, saying it would be in Byrhtnoth's interests to buy peace, rather than to engage in battle. Byrhtnoth replies that he will not give up without a fight, and orders his men to take up positions along the river-bank. At length, the tide recedes, exposing a narrow causeway.
The favourite suggested site for this encounter is the causeway which, at low tide, still connects Northey Island (less than two miles downstream from Maldon) to the south bank of the Blackwater. However, there has been no archaeological evidence to support the identification.
The English fiercely defend the ford, pinning-down the Vikings on the other side of the river. The Vikings decide on a change of tactic, and, playing on Byrhtnoth's pride, goad him into letting their infantry across.
It may seem like an act of total folly, to have let the Vikings cross the causeway - the poet's tone certainly seems to be critical. On the other hand (assuming that the poem really is a true reflection of what happened), if Byrhtnoth had simply maintained his position, the Viking fleet might well have put to sea, to land elsewhere. Byrhtnoth may have believed that bringing them to battle at this time was his best chance of victory.
Battle is joined. In due course, Byrhtnoth is killed.
A late-12th century history of Ely (Byrhtnoth was a patron of Ely), the 'Liber Eliensis', which weaves a somewhat unlikely yarn around the battle of Maldon, says that the Vikings carried off Byrhtnoth's head as a trophy. The abbot of Ely, and some of his monks, collected Byrhtnoth's remains from the battlefield, and took them back to Ely for burial - replacing his missing head with a wax ball. The 'Liber Eliensis' also implies, strangely and incorrectly, that Byrhtnoth was ealdorman of Northumbria. This oddity is carried on in the inscription which marks Byrhtnoth's final resting place (to which he was moved in 1771), where he is described as "Northumbrior. Dux".
The cowardly Godric flees from the battle on Byrhtnoth's horse. Many others, thinking that it is Byrhtnoth who is fleeing, themselves run away. The poem closes with Byrhtnoth's faithful followers fighting to the bitter end.
'The Battle of Maldon' can be found, in Old English and in Modern English interpretations, on the Faculty of English website of the University of Oxford.