Percy Bysshe Shelley: poet, atheist, and determined opponent of the over-powerful. What would he have made of the dramatic resignation this week by Boris Johnson after weeks of his authority ebbing away? A flight of fancy of course, but an irresistible one for me, whose working life these last days and weeks has been dominated by the disintegration of Johnson’s credibility. All the while I’ve been preparing – in my downtime – to commemorate 200 years since the death of a titan of English poetry and a political radical.

Like the outgoing prime minister, Shelley went to Eton, but the common ground stops there. He was a rebel at heart, distrustful of authority, and raged at abuses of power by what he saw as the unaccountable and heartless establishment. Perhaps his most famous poem, Ozymandias, mocks the empty legacy of a puffed-up despot. Meanwhile England in 1819, written in the last year of the reign of George III who had for years been mentally incapable, tells of “Rulers who neither see nor feel nor know, But leechlike to their fainting Country cling”.

The Mask of Anarchy satirises the government of the day as the epitome of anarchy and injustice, and ends with an impassioned appeal for ordinary people to rise up: “Ye are many, they are few.” Shelley was thrown out of Oxford in connection with his essay The Necessity of Atheism, and he strongly believed in poetry as a powerful force for political good. “Poets are the unacknowledged legislators of the world,” he wrote. For Shelley, the poetic was political.

Part of Shelley’s allure is the people who surrounded him. His wife was Mary Shelley, daughter of another political radical, William Godwin, and Mary Wollstonecraft, generally recognised as the mother of British feminism. At the age of 18, Mary wrote Frankenstein, an astonishingly mature work about the hubris of an irresponsible inventor who creates the first of a new race but denies its human needs – with catastrophic consequences. At this time, Percy and Mary were living and travelling with Lord Byron and Mary’s half-sister Claire Clairmont, a formidable ménage of literary creativity.

Shelley’s politics were progressive, as were his political attitudes towards women. He was an ardent supporter of female emancipation and of gender equality, and had a profound respect for the work of Mary Wollstonecraft. His personal relations with women were less respectful. Shelley abandoned his 19-year-old wife, Harriet Westbrook, and their two children in 1814 to elope with the 16-year-old Mary. Two years later Harriet drowned herself in the Serpentine in London. In the two years before he died – a dark and difficult time when Mary endured repeated miscarriages and the death of their small son – he wrote tender poems about Jane Williams, the wife of his friend Edward. Whether this infatuation would have led anywhere will remain unknown; Shelley and Edward both drowned off the coast of Liguria in north-west Italy on 8 July 1822 after a violent squall hit their small boat. Shelley’s body was identifiable only by the collection of Keats poems found in his jacket pocket.

They all died young, these second-generation Romantic poets – Shelley at 29, Keats at 25, Lord Byron at 36. As I was growing up, it was Keats’ work that was the most compelling – a yearning and eager poetry that had a youthfulness about it, much of it focused on the process of desire, and with an aesthetic wish to capture and fix desire through art. But Shelley fascinates through his complexity – his reformist zeal is matched by a strong sense of personal gloom and pessimism, which he works through in his poetry, using nature as a counterpoint to his human suffering. If Keats was a first love, Shelley is a mature one.

A few weeks ago, a group of us went on a visit to the Italian resort of Lerici, where Percy and Mary had their last home in the Casa Magni before his untimely death. Shelley was haunted by visions of himself – a doppelganger he saw from the balcony of the Casa Magni – and in a park next to the house we listened to readings of his poetry by, among others, the poet laureate Simon Armitage, and imagined him there. In a few weeks’ time, we will go to the non-Catholic cemetery in Rome, where Shelley and Keats are buried, to commemorate him once again.

Ozymandias, “king of kings”, left no legacy whatsoever; the opposite is true of the man who created him.

• Reeta Chakrabarti is a Trustee of the Keats-Shelley Memorial Association, which oversees the Keats-Shelley House in Rome, and a patron of Keats-Shelley 200