The realisation that one might be show-offy in a good way is among Donne’s chief bequests to English literature, a salutary corrective to the 16th-century cult of Sidneian sprezzatura. The embrace of effort – the wish to impress, to delight, to dazzle, to convince or convert, and the willingness to be seen working at it – is the secret to the deathless charm of ‘The Flea’ and the pathos of the ‘Holy Sonnets’.