Dorothy Wordsworth (1771-1855) was the younger sister of the great Lakeland poet, separated from him as a child after their parents died. In their twenties they were reunited and spent the rest of their lives together.

Coleridge called her a genius, and William repeatedly stressed her importance to him: “She, in the midst of all, preserved me still/ A poet.”

Dorothy wrote few poems but left vivid and entrancing letters and journals describing natural history, their community, and their shared lives. She had no wish to be published and does not seem to have wanted a husband.

After Coleridge drifted away and William married, the Wordsworths and his wife Mary became a different kind of threesome.

Coleridge accused him of “living wholly among Devotees – having every the minutest Thing, almost his very Eating and Drinking, done for him by his Sister, or Wife”.

There is some truth in this. This highly gifted woman spent much of her life copying her brother’s poems and looking after his children, and she was not included in the Dictionary of National Biography until 1993. Yet, as her biographer says: “Her tastes were easily satisfied, and a lakeland walk or a coach ride by moonlight would furnish her mind with unforgettable impressions.”

Lucy Newlyn, an Oxford professor and a fine poet herself, has written the first book to give the brother and sister equal attention. William and Dorothy, she argues convincingly, “made an incalculable contribution to each other’s writing”, and her work for him was “not in any sense an act of subservience”.

She criticised his early poems for being too difficult, encouraging him to write in plain pure English and to commemorate the obscure lives of shepherds and vagrants.

She had the strongest sympathy with the poor and struggling people around them, and one of her finest works is A Narrative of George and Sarah Greene. These were two people who had died on the fells and the essay was written to raise money for their orphaned children.

William wrote immortal poetry, Dorothy wrote prose, but as William argued, the two genres belong to the same family.

This is an immensely valuable book. It convinces me that Dorothy was not exploited by her brother but created a lifestyle which was good for them both. Without him, she might well have spent her life as someone’s housekeeper, while he might well have been a lesser writer without her.

* William and Dorothy Wordsworth:
All In Each Other
by Lucy Newlyn is published by Oxford University Press, £19.99