JRR Tolkien and his wife Edith Tolkien are buried together in Wolvercote cemetery in north Oxford. Along with their names, the grey Cornish granite head stone is inscribed with two further monikers: Beren for Tolkien and Luthien for Edith.

The story of Beren and Luthien makes up the central tale of The Silmarillion – a precursor to the epic story narrated in The Lord of The Rings. Although the two works inhabit the same mythopoeic universe, they are written in completely different styles – whereas The Lord of The Rings is all wonderful story-telling, fine detail and long conversations, there is virtually no descriptive foregrounding in The Silmarillion, the men and elves that populate its pages are heroic, mysterious, with psychological depth derived by virtue of their great deeds.

The Lord of The Rings is of course one of the highest selling books of fiction ever written, with over 150 million copies sold worldwide and has won fans as various as Joni Mitchell and her husband Chuck Mitchell, who were so impressed by the Trilogy that they founded a publishing company called Gandalf, the philosopher and novelist Iris Murdoch, who wrote “I have been delighted, carried away, absorbed by The Lord of the Rings” in a fan letter to Tolkien and poet W.H. Auden, who came up to Oxford one generation later than Tolkien (“The War of the Ring is one of the very few books which I shall keep re-reading all my life”).

The Silmarillion was published posthumously, with several of the stories filled in by his son Christopher from notes and half-finished manuscripts. On release, it was poorly reviewed: Robert M. Adams of The New York Review of Books called the work “an empty and pompous bore”; The New Statesman’s Peter Conrad noted (rather glibly) – “Tolkien can’t actually write.”

It’s easy to see why The Silmarillion is so unloved – it’s so full of incomprehensible names, the warrior Turin Turambar, the elf stronghold Nargothrond, Thingol Thranduil, King of the woodland elves that it can get a bit confusing at points – so he’s so and so’s brother? Ah right.

So why did Tolkien choose two characters from his supposedly inferior work to adorn his grave? After all, there are plenty of wonderfully convincing relationships in The Lord of The Rings Trilogy: Faramir of Gondor and Eowyn or Rohan, the elves Celeborn and Galadriel, Aragorn and his elf-queen Arwen or even the hobbits Sam Gamgee and Rosie Cotton.

It is also a far more unforgiving text – while The Lord of The Rings builds on the harsh moral universe of Anglo-Saxon epic with a Christian gloss that speaks to themes of redemption, healing and divine guidance (as he dies Theoden, King of Rohan, says: “I go now to the halls of waiting to sit beside my fathers, until the world is renewed”), The Silmarillion tells a far darker story – fortune wrecks the best-laid plans and the Gods have retreated from the world.

The story of Beren and Luthien holds the key to why the Silmarillion should not be neglected, but read alongside the epic of the ring.

Beren is a mortal man. One day walking in the woods in the evening time he sees Luthien, an elf, dancing “upon the unfaded grass.” He falls in love, and she with him. But there is trouble ahead – her Father, the elf-king, who cannot bear to see her with a mortal man, tells Beren that he can only win her hand if he brings him a Silmaril, a precious jewel made by the elvish master craftsman Feanor, which has been stolen by the evil Morgoth, who has Sauron (remember him? Turns into an enormous eye) as a servant.

Beren and Luthien recover the jewel but at great cost, dying in the attempt. Aragorn takes up the story in The Fellowship of The Ring: “It is sung that they met again beyond the Sundering Seas, and after a brief time walking alive once more in the green woods, together they passed, long ago, beyond the confines of this world.”

Aragorn is mortal but he too loves an elf, Arwen. And he too is set a task by her Father who decrees that only the King of Gondor can marry her, the kingdom to which he is heir. His many tasks and efforts culminate in his ascent to the throne after Sauron is defeated at the last when the ring is destroyed.

In the great epic of Roman civilization, Virgil’s Aeneid, there is constantly a kind of double vision at work – when Aeneas grasps the golden bough that unlocks the underworld, you feel history folding around his hand. In a moment, he opens the way to the founding of Rome and to the future of an Empire.

Tolkien too has the gift of this double vision and indeed his synthesis of the stories of Beren, Luthien, Aragorn and Arwen leaked into the experience of his own great love. He wrote of his love for Edith: “For ever (especially when alone) we still met in the woodland glade, and went hand in hand many times to escape the shadow of imminent death before our last parting.”