A Source for Robert Browning's A Likeness

This article suggests that an incident recalled in a recently published letter of Robert Browning's to his friend Lady William Russell might be a source for his poem 'A Likeness', first published in Dramatis Personae (1864). The letter concerns a portrait of Lady William by Browning's friend Seymour Kirkup. The letter also links the poem to the late 1850s, and so helps to clarify the order in which the poems in Dramatis Personae were written.