It's a perfect moment, what with the upcoming referendum and the 700th anniversary of Bannockburn, to revisit a - perhaps the - foundational work of Scottish literature.

There hasn't been a new edition of The Brus that I know of since AAM Duncan's valuable but error-strewn parallel text of 1997. New readers will encounter a verse chronicle of some 13,600 lines, and a text that combines elements of romance, philosophical homily, political spin and the lineaments of modern biography, together with thoughts on the function of literature.

What they will not find is ­arachnology. The Bruce encountered a few scorpions along his chequered way but the story about the spider is a homespun legend borrowed later to illustrate the future king's doggedness.

Barbour remains fairly shadowy: born around 1320, presumably to a barber father, possibly in Aberdeen but just as likely in Galloway.

After serving as deacon in Dunkeld, he was promoted archdeacon in Aberdeen. He may have studied at Paris, Avignon and Oxford, and was favoured when David II was freed on ransom in 1357.

For the rest of his life, Barbour seems to have served the Scottish court. He received a stipend from Robert II for writing the poetic life of his grandfather. Like the Gospel writers, Barbour had no direct experience of his subject and wrote some 30 years after the deaths of its main chivalric subjects, Robert the Bruce himself and Sir James Douglas.

"A! Fredome is a noble thing / Fredome mays maan to haiff liking / Fredome all solace to man giffs / He levys at es that frely levys." These are certainly the best known lines of Barbour's, and for many the only lines known.

As such, they usefully capture the plain vigour of his prosody (rhymed but with elements of alliteration retained) and his ability to turn a general point without weightiness or sententious philosophising.

How free is James Higgins's "free translation" can be gauged from Book 1, ll.225-226: "Ah, freedom is a most noble state, / freedom lets a man savour life's taste . . ." Barbour himself often "sprang" his octosyllabic couplets. In following that, Higgins places the poem very acutely at a point where oral declamation gives place to literary reading.

It's a text to be read aloud, but also to be absorbed silently, and the very opening lines, with their meditation on the pleasures of narrative, point in that direction. It's worth remembering that Chaucer was some 20 years younger than Barbour and working under the protection of a more highly developed and secure court administration.

Whether The Brus needs to be "translated" for modern readers is a moot point. Once you're alert to the French borrowings, it flows easily enough, but many lines meet the eye awkwardly.

"Leawté to liff is gretumly / Through leawté liffis men rychtwisly" is given by Duncan as "Loyalty is to love wholeheartedly, by loyalty men live righteously" and by Higgins as "Loyalty is love unreserved, loyalty makes men be honest." But it isn't fair to compare the two versions item by item.

The tone of Higgins's translation is just right, combining learnedness with a vernacular impatience, delivering the set-piece of Bannockburn (though I'm sure even the original is full of inauthentic cinematic add-ons to make the victory seem all the more dramatic) with real vigour.

The latter books, subsequently added, limp a bit in every version, and one senses Barbour reaching for complimentary effects, his eye on a more generous pension. The original payment was just £1, though there was a later one of £10, which may have been for some dynastic flannel called Stewartis Oryginalle.

The point is that nobody really knows. Barbour's great poem doesn't come out of the dark with quite the mysterious, collective-unconscious force of Beowulf. It's a work of obvious historical provenance - the still-precarious court of Robert II - and by a named author.

But it has something of the same quality, folkloric but subtle, atavistic but also "modern". It's a great story, convincingly and ringingly retold, and Higgins gives it just the right amount of modern underscoring to make it sing as well.