As Rik Myslewski quipped recently "In other news, Pope Benedict XVI has been revealed to be a Roman Catholic, and a common ursus americanus was discovered relieving himself in a shady copse."
With a title like Secret sex poems 'key to 18th Century book's success' you'd expect fatuous twaddle and—despite the fact that this is the BBC, and not The Daily Mail—fatuous twaddle is what you get.
But, despite the BBC, there is a genuine story here.
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In my database of eighteenth-century erotica I include eighteen editions (to 1801) of The Works of the Earls of Rochester, Roscomon, And Dorset: Also those of the Dukes of Devonshire, And Buckinghamshire to which are added, The Cabinet of Love, And several other Poems On diverse Subjects.
This collection changed from edition to edition, ranging from three poems (1714), to thirteen (1735). The thirteen titles in the 1735 collection are: “The Discovery,” “Arbor Vitae” [two cantos], “Dildoides,” “The Delights of Venus,” “Lord Rochester against his Whore-Pipe,” “An Interlude,” “A Panegyrick upon Cundums,” “Satire on a Whore,” “Advice to the Kind Ladies,” “Mrs Knight’s Advice,” “The Insatiable,” “A Drinking Song” and “The Anniversary.”
The Cabinet of Love has been of intermittent scholarly interest since at least 1927 when many of the poems were listed in Johannes Prinz, John Wilmot Earl of Rochester, His Life and Writings With His Lordship’s Private Correspondence, Various Other Documents, And a Bibliography of His Works and of The Literature on Him (Leipzig: Mayer & Müller, 1927).
Dr Claudine van Hensbergen may indeed be "the first" attribute "the success of The Works" to the bawdy poems, as the BBC article states. It is a bold claim, but I am inclined to agree. Certainly the collection with the bawdy poems was popular, at least as popular as the version of The Works of the Earls of… without The Cabinet.
When I started researching this collection I assumed—as others have—that this anthology was the clandestine edition of The Works Of the Earls of… and that the version without The Cabinet of Love was the edition openly published and advertised. This suggests that the bulk of the market for The Works of the Earls of… was satisfied by the legitimate edition lacking The Cabinet of Love, and that only a few brave/debauched souls would want the clandestine edition with The Cabinet of Love. What I found is that the two versions seems to have been equally successful and they were both openly advertised, or at least, advertised equally as often.
Dr van Hensbergen is also quoted as claiming that "the circulation of The Cabinet alongside The Works of the Earl of Rochester helped cement his scandalous reputation"—which also seems possible from my research.
Obviously, Rochester would have his scandalous reputation without The Cabinet of Love. No question. But almost all of his eighteenth-century readers encountered his works beside those Roscomon, Dorset, Devonshire, and Buckinghamshire, and roughly half of his eighteenth-century readers also encountered his works beside those in The Cabinet of Love—even though the poems in The Cabinet of Love were clearly not attributed to him, or any of the other named Dukes. These other works provide the context: naughty Rochester, poet of the naughty times of the naughty Charles II. If you read Rochester, you are a naughty, naughty boy.
Of course it is stupid to claim "The success of … was down to pornographic poems hidden in the book"—the poems weren't hidden, and they were far from being the sole attraction of the collection. But, to be fair, that is likely the work of the breathless—and anonymous—BBC writer, not Dr van Hensbergen. The same breathless—and anonymous—BBC writer who added "depth" (and a photo) to their article with the observation that "In [the] 2004 film The Libertine, the notorious Earl … was played by Johnny Depp."
[UPDATE 23 October 2013: two editions of "The Cabinet of Love" are now available on Google Books; you will find them here in my (sporadically updated) list of "Eighteenth-Century Erotic Texts Online."]