THEY HAVE BECOME A famous couple, like Hero and Leander or Pyramus and Thisbe. Their relationship was of the mind rather than of the body, but it had its comic as well as its romantic moments.

For a while they needed each other; they were, in the Platonic sense, split halves of a soul that had to be reunited before it could properly manifest itself. That soul became the source of English Romantic poetry. Such a miraculous union — that of Wordsworth and Coleridge — could not last for ever.

“William has a great attachment to poetry,” his sister Dorothy Wordsworth wrote at the very beginning of his career, “which is not the most likely to produce his advancement in the world.”

And so it proved. He merely “passed” at university, then set off on a series of desultory wanderings. All paths seemed to lead to France, in the middle of its bloody revolution. He cut short his hair. He fell in love with, and impregnated, his French mistress. He became a convinced democrat and radical. In this he was not unlike a thousand of his contemporaries.

One of those, two years younger, was Samuel Taylor Coleridge. He was similarly convinced of the efficacy and significance of the French Revolution. He signed one of his letters “with the ardour of fraternal friendship”. He described himself as a “dreamer” and as “fretful and inordinately passionate”. By the time he reached Cambridge he was addicted to laudanum, the drug that became the magic theatre of his life.

In 1794, at the age of 24, Wordsworth told a friend that “I have been doing nothing and still continue to be doing nothing, what is to become of me I know not”. Although he had published two poems he had, as yet, no sense of his genius. Coleridge was in a similarly disgruntled state. He had joined the Army under the pseudonym of Silas Tomkyn Comberbache to escape his university debts; he was discharged as insane before returning to Cambridge. Here he was involved in extravagant notions such as the idealised community known as Pantisocracy.

Both young poets were still passionately committed to the ideas and ideals of the revolution; the “Terror” and the fall of Robespierre did not materially affect their enthusiasm. It had, in fact, become their faith. But otherwise they were lost in the world. They had no income, no future, no prospects to speak of. Coleridge married, and subsisted by public lecturing. Wordsworth received hand-outs from friends and relatives.

They first encountered one another in Bristol, in the late summer or early autumn of 1795. It is not perhaps surprising that there are three different and irreconcilable accounts of their meeting; so myths are made. The effect, however, was clear. They impressed each other terrifically.

Wordsworth described Coleridge’s conversation as “a majestic river, the sound or sight of whose course you caught at intervals”. Wordsworth recited his poetry to his new acquaintance, which Coleridge deemed to manifest “the union of deep feeling with profound thought”.

Soon they were discussing everything — poetry, politics, plans for the future. They settled near each other in the West Country. They read each other’s works, making criticisms and suggestions. They collaborated. They declaimed aloud as they walked down country roads.

They were inseparable, Coleridge spending many days away from his wife and family to be close to Wordsworth. As he put it in one of his notebooks, “the flames of two candles joined give a much stronger light than both of them separate”.

Together they created a new form of English poetry. The fruit of their labours in the West Country, Lyrical Ballads, was a new volume for a new age of revolution. But theirs was not a political gesture. It was a deeply creative response to the doctrines of equality and liberty promulgated by the French revolutionaries.

Wordsworth and Coleridge were relocating dignity in the commonplace, restoring grace and significance to ordinary lives where saints and heroes walked unannounced and unknown. They were proclaiming a democratic world in which outcasts had as much right to be heard as anyone, and in which women and children had a voice.

The Friendship is an elegant tour d’horizon, a scholarly and charming summary of an often explored partnership.

On a critical or analytical level, it is perhaps familiar; but Adam Sisman is good at recording the complicated human relationships between all concerned. There is the problem of Coleridge’s wife, for example, who resented the amount of time that her husband spent with the Wordsworths. And there is Dorothy Wordsworth, caught in the difficult position of a worshipping sister.

Sisman has done his research thoroughly, and is good at disentangling a confusing chronology: in this narrative the two poets march side by side on their journey towards fame and literary glory.

But eventually they drew apart. There were growing differences. Wordsworth was egotistical and oversensitive; he could never bear even the mildest criticism. Coleridge, on the other hand, suffered from inanition and self-disgust.

He willingly prostrated himself before his companion, comparing himself to John the Baptist before Christ. But he did not see matters clearly from that semi-recumbent position. He let Wordsworth excise many of his poems from the second edition of Lyrical Ballads. His confidence in his poetry was wholly gone. He became ill, and took increasingly to opium. The great slide of his life had begun.

When Coleridge returned to England, after a period of dithering in Malta and in Italy, the Wordsworths had never seen a man so changed. Drink and opium had glazed him; he was bloated and pale. He no longer had a commanding eye, but had become introverted and remote.

Then came the final break. A mutual friend, in a fit of rashness, blurted out certain truths that Wordsworth had confided to him — in particular that Coleridge had become a drunkard and a “nuisance”.

Coleridge felt betrayed, and bitterly resented Wordsworth’s ingratitude. They met intermittently over the remaining years but their intimacy — their joy in one another’s company — had vanished.

It is a sad story without a moral except, perhaps, for the obvious one that youthful enthusiasm and youthful friendship are bound to fade — that advancing years do not necessarily bring happiness or contentment — that the greatest careers are accompanied by a sense of disappointment. Only the work of art, as Wordsworth and Coleridge knew, is satisfyingly complete.

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