In Footsteps: Adventures of a Romantic Biographer, Richard Holmes described how, aged 18, he followed the route taken by Robert Louis Stevenson and his donkey almost 100 years earlier as they walked through the Massif Central in France. Sleeping, as Stevenson did, beneath the stars, bathing in rivers, and feeling half mad on the excess of liberty, Holmes learned that his vocation was to live like a ghost crab in another man’s shell. No one has described better the strange and obsessive nature of biographical pursuit, and the business of “footstepping” has since become associated with the Holmesian style of method-biography, in which the biographical subject returns from the dead with a palpable physical presence.

Adam Nicolson makes plain his debt to Richard Holmes: “I think of this book as a tributary to the great Holmesian stream,” he says in the introductory chapter to The Making of Poetry. “Its method is his: to follow in the footsteps of the great, looking to gather the fragments they left on the path, much as Dorothy Wordsworth was seen by an old man as she was accompanying her brother on a walk in the Lake District, keeping ‘close behind him, and she picked up the bits as he let ’em fall, and tak ’em down, and put ’em on paper for him’.”

The image of Nicolson as Dorothy, picking up the lines dropped on the road by Wordsworth as he went “bumming and booing” about, is wonderfully apt not least because Nicolson’s own sensibility – his ear, his eye, his sense of place and the intensity of his concentration on words, plants, foliage and light – recalls that of Dorothy Wordsworth. The Making of Poetry is indeed a tributary to the great Holmesian stream, and also a tribute to the Romantic art of observational note-taking.

Nicolson’s aim is to get as close as possible to the sources of Wordsworth and Coleridge’s poetic power in 1797-98, when they collaborated on Lyrical Ballads: he therefore moves to the Quantocks. From the landforms and settlements of the landscape, he traces what he calls “the deep psychic structure of the year”, which he defines as a series of departures and arrivals, a restless journeying, a to-ing and fro-ing, as a host of itinerants wander up and down roads, telling stories and going nowhere in particular.

The book begins, however, with the most famous arrival in literary history. Having walked from Nether Stowey to Racedown, the West Dorset home of the Wordsworths, Coleridge leaps over the gate and bounds through the field to where William and Dorothy are working in their garden. He is 24 and nearly famous; Dorothy is 25 and on the run; Wordsworth is 27 and pregnant with poetic genius: bliss it was to be alive that dawn but to be young was very heaven. Except that 1797 was neither bliss for Wordsworth and Coleridge nor very heaven – the friendship that evolved was the prelude to a tragedy, and Nicolson is alert to the fault-lines.

When they met, Wordsworth was weak and Coleridge was strong; by the end of the year this was to be reversed. The Wordsworth whom Coleridge discovered in Racedown was recovering from a breakdown: having returned from Revolutionary France where he had sired a daughter, he was now living, in a mock-up of the French family he had abandoned, with his sister and the five-year-old son of a friend. Coleridge, meanwhile, effectively abandoned his own wife and child in order to devote himself full time to Wordsworth-worship.

He would later move his family to the Lakes in order to be on Wordsworth’s native soil, but the Wordsworths now moved to Alfoxden, two miles from Nether Stowey, to be nearer to Coleridge. “Walks extend for miles over the hilltops,” Dorothy wrote of their new home, and it was on these walks that Lyrical Ballads was born.

The “driving and revolutionary force of this year”, Nicolson says, was the idea that “poetry was not an aspect of civilisation but a challenge to it; not decorative but subversive, a pleasure beyond politeness”. A “lyrical ballad”, Nicolson explains in a brilliant analysis of the poems, combines “the storytelling and quick rhythms of the ballad with the close emotional focus and intensity of lyric poetry”. Using the language of everyday speech, Coleridge would describe the supernatural world and Wordsworth the natural world but both poets, Nicolson shows, relied on narrators who were in equal measure loquacious and uncertain; the poems “retract from reliability in the way a snail’s horns pull back when touched”. It is a memorable image and the retraction is equally true of Wordsworth and Coleridge themselves, when a biographer comes anywhere close.

The year belonged to Coleridge: he was the genius of the heath and oakwoods of this corner of Somerset where the Ancient Mariner was born, and it was his glistening eye that made Nether Stowey the centre of connectivity. Coleridge’s project was to bring together “a small company of chosen individuals” whose task was to rejuvenate the poetry and politics of the age: these included Charles Lamb, whose sister had recently lost her reason and murdered their mother; John Thelwall, hero of the 1794 Treason Trials; and the young William Hazlitt, described by Coleridge as “singularly repulsive; brow-hanging, shoe-contemplative, strange”. Heaven knows where they all slept in the miniscule Coleridge cottage but each member of the circle was, as Nicolson points out, already on the edge of madness. It is hardly surprising that this dishevelled crew, walking, talking, arguing in all weathers and at all times of day and night, attracted the attention of the government, which assumed they were spies.

Every glimpse of Coleridge is charming but none more so than when we see him in his garden up to his waist in weeds, explaining to Thelwall that weeds too are entitled to their liberty: “I thought it unfair in me to prejudice the soil towards roses and strawberries.” It is hard to catch the charm of Wordsworth, but Nicolson offers some different perspectives: Wordsworth, he reminds us, was something of a dandy in his silk waistcoats and embroidered coats, and his face, as Hazlitt noticed, was “inclined to laughter around the mouth”. His laugh, when it came, apparently sounded lecherous. What Nicolson shows us is the setting into stone of the Wordsworthian ego. The image of the all-powerful poet, he suggests, is caught by Coleridge in the demonic figure of Kubla Khan.

Lyrical Ballads opened with a voyage out – the Ancient Mariner bursting into frozen seas – and closed with Wordsworth returning after five years to the view above Tintern Abbey on the River Wye. The most striking feature of the sublime “Lines Written Above Tintern Abbey”, Nicolson suggests, is the absence of Coleridge, whose guidance had ensured that Wordsworth arrived at his destination. Inverting this pattern, The Making of Poetry opens with a destination and closes with a sea-voyage: the Wordsworths and Coleridge on the packet boat to Germany in September 1798, having deposited Lyrical Ballads with a radical Bristol publisher.

While Coleridge is captivating his audience on deck, Wordsworth is suffering from seasickness down below. Their paths have forked and their footsteps, from now on, will diverge. Adam Nicolson has shown us, in this subtle and masterly book, the cost of the making of poetry.

Frances Wilson’s books include “The Ballad of Dorothy Wordsworth” (Faber & Faber)

The Making of Poetry: Coleridge, the Wordsworths and Their Year of Marvels

Adam Nicolson

William Collins, 336pp, £25