This brought her two stepsisters: Godwin's daughter, later Mary Shelley, only eight months her senior, and his stepdaughter Fanny Imlay, a couple of years older.

Both parents were well-educated and they co-wrote children's primers on Biblical and classical history, and ran a bookshop and publishers known as the Juvenile Library.

She contrived to send her volatile and emotionally intense daughter to boarding school for a time, so providing her with more formal education than her stepsisters.

Clairmont aided her stepsister's clandestine meetings with Percy Bysshe Shelley, who had professed a belief in free love and soon left his own wife, Harriet, and two small children to be with Mary.

The three young people traipsed across war-torn France and into Switzerland, fancying themselves as characters in a romantic novel, as Mary Shelley later recalled, but always reading widely, writing, and discussing the creative process.

Clairmont's emotions were so stirred by Cordelia that she had one of her "horrors", a hysterical fit, Mary Shelley recorded in her own journal entry for the same day.

Clairmont later followed up her letters with visits, sometimes bringing Mary, whom she seemed to suggest Byron might also find attractive.

Byron, in a depressed state after the breakup of his marriage to Annabella Milbanke and the scandal over his relationship with his half-sister Augusta Leigh, made it very clear to Clairmont before he left that she would not be a part of his life, but she remained determined to change his mind.

She convinced Mary and Percy Shelley that they should follow Byron to Switzerland, where they met him and his personal physician, John William Polidori, at the Villa Diodati by Lake Geneva.

At first he maintained his refusal of Clairmont's companionship and allowed her to be in his presence only in the company of the Shelleys; later, they resumed their sexual relationship for a time in Switzerland.

"[9]He referred to her also in a letter to Douglas Kinnaird (20 January 1817): You know – & I believe saw once that odd-headed girl [Claire Clairmont] – who introduced herself to me shortly before I left England – but you do not know – that I found her with Shelley and her sister at Geneva – I never loved her nor pretended to love her – but a man is a man – & if a girl of eighteen comes prancing to you at all hours of the night – there is but one way – the suite of all this is that she was with child – & returned to England to assist in peopling that desolate island...

Clairmont took up residence in Bath and in January 1817 she gave birth to a daughter, Alba, whose name was eventually changed to Allegra.

Clairmont felt that the future Byron could provide for their daughter would be greater than any she herself would be able to grant the child and therefore, wished to deliver Allegra into his care.

Their friend Thomas Jefferson Hogg joked about "Shelley and his two wives", Mary and Claire, a remark that Clairmont recorded in her own journal.

Clairmont was also entirely in sympathy, more so than Mary, with Shelley's theories about free love, communal living, and the right of a woman to choose her own lovers and initiate sexual contact outside marriage.

[14][15] In Shelley's "Epipsychidion", some scholars believe that he is addressing Clairmont as his:[9] Comet beautiful and fierce Who drew the heart of this frail Universe Towards thine own; till, wrecked in that convulsion Alternating attraction and repulsion

Thine went astray and that was rent in twain.At the time Shelley wrote the poem, in Pisa, Clairmont was living in Florence, and the lines may reveal how much he missed her.

She also insisted: I am perfectly convinced in my own mind that Shelley never had an improper connexion with Claire... we lived in lodgings where I had momentary entrance into every room and such a thing could not have passed unknown to me...

I do remember that Claire did keep to her bed there for two days – but I attended on her – I saw the physician – her illness was one that she had been accustomed to for years – and the same remedies were employed as I had before ministered to her in England.

She paid for Clairmont to travel to her brother's home in Vienna where she stayed for a year, before relocating to Russia, where she worked as a governess from 1825 to 1828, firstly in St Petersburg and then in Moscow.

At one point, she thought of writing a book about the dangers that might result from "erroneous opinions" about the relations between men and women, using examples from the lives of Shelley and Byron.

She lived in Paris for a time in the 1840s, where she attended Harriet de Boinville's social gatherings, crowded with republicans and Italian revolutionaries.

In one letter to her stepsister, Mary, she wrote:"At Madame de Boinville's the people are clever and I go there and I like the conversation, but I am never allowed to speak myself... after fifteen years being silent, I want to talk a good deal... to clear out my mind of all the ideas that have been accumulating and literally rotting there for so many years – but they won't allow me this in Rue Clichy – the instant I speak, the whole coterie fall upon my words and pick them to pieces... seize upon my argument (so dear to me)... they are liberals of such opposite characters...

The Aspern Papers by Henry James is inspired by the true story of a retired captain, Edward Silsbee, who tried to purchase the letters that Shelley had written to Clairmont, and which she saved until her death.

Clairmont died in Florence on 19 March 1879, at the age of 80[15] having outlived all the members of Shelley's circle except Trelawny and Jane Williams.

Writing for the Wordsworth Trust in 2014, author Lesley McDowell described Clairmont as "the ideal Romantic woman, as conjured up by Mary Wollstonecraft herself in A Vindication of the Rights of Woman", adding that "rarely did any other Romantic figure “mix in the throng” and attain knowledge of herself through others, to the extent that Claire Clairmont did.

"[27] The 1816 trip to Switzerland during the Year Without a Summer, during which Clairmont aimed to reunite with Byron, and Mary Shelley began writing Frankenstein, is the focus of multiple modern re-tellings in several mediums.

Thirty years later, Clairmont was played by Bel Powley in Mary Shelley (2017) and by Nadia Parkes in the Doctor Who episode "The Haunting of Villa Diodati" (2020),[28][29] Clairmont was depicted in a special edition of the comic book The Wicked + The Divine, as an incarnation of the goddess Inanna and a member of the 1830s Pantheon.