The Phi shelfmark was invented by the Bodleian in 1882 to demarcate (and restrict access to) books deemed potentially corrupting to young minds. Typical and ridiculous Victorian prudishness, you might think, but the fact is the Phi collection grew. This was inevitable in part since the Bodleian is a copyright library, but librarians also went to some lengths to gather copies of important works and keep them safe. In fact it's a balance of safeguarding the innocent, but also the books themselves, which perahps explains why the Phi mark was only derestricted quite recently.
There are something like 3000 works in the Phi collection, and 20 notable items are currently on display in one of the cases in the Weston Library foyer. These include books banned for a variety of reasons - explicit illustrations, homoerotic or obscene content, comedic works like the Pop-up Kama Sutra, sex manuals, works ancient and modern. They provide an interesting snapshot of what different generations have considered corrupting.
One thing you might not have expected to see in the collection is Oscar Wilde's The Picture of Dorian Gray. Wilde's own life was probably a factor in its restriction, though a homoerotic subtext didn't help. Though it was never formally banned by the censors, the novel did have to go through several revisions, cutting out a lot of its original content to make it acceptable for publication, and even then WH Smiths withdrew all their copies from sale. Thus it earnt its place on the Phi shelves.
In an interesting twist, because the display is in the foyer and might be seen by those unprepared for the content, it has been cordoned off with warning signs. A nice compromise between free access and sensibilies, but also maybe a sign we haven't moved so far from the considerations of those Victorian librarians after all.
