It could be that I’ve only just started paying attention, and that actually this isn’t a new trend at all, but it feels to me like London theatre has been on a ‘lost’ plays bender for the last few months. Whether it’s world premieres of works by great masters of 20th-century playwriting (Tennessee Williams’s I Never Get Dressed Till After Dark on Sundays and A Cavalier for Milady), rediscoveries of once successful but since forgotten pieces (Graham Greene’s The Potting Shed and anything by Terrence Rattigan), or grand stagings of impossibly ambitious world-historical plays (Ibsen’s Emperor and Galilean), a piece of 'lost' theatre seems to be opening every other week at the moment.

But are these plays really worth ‘finding’, or is it sometimes better for ‘lost’ plays to stay that way? If something hasn’t been put on for years and years, or indeed has never been put on at all, there might just be a good reason why.

There’s an argument that any play by a great writer – Williams, Ibsen, Rattigan, whoever – is worth bringing to the stage for theatrical-historical interest alone. The more works by a playwright that we see, the greater the understanding we’ll gain of the rest of his or her oeuvre. This is the logic behind Gene David Kirk’s passion for staging unseen works by great writers at the Jermyn Street Theatre. The problem with this argument is that, in reality, only a minority of theatregoers will value a piece of work for the light it sheds on a particular strand of theatrical discourse; most people have fairly simple desires from the theatre they see – they want to be entertained.

Now, I didn’t much enjoy Kirk’s recent production of A Cavalier for Milady, a play written by Williams in 1980 but only receiving its world premiere this year at the Cock Tavern prior to a transfer to Jermyn Street. The play itself felt unresolved, more of a sketching out of ideas than a proper attempt at narrative drama, and I found the staging old-fashioned and overly literal. I could see how a Williams obsessive might relish the opportunity to see this strange piece, but it pretty much left me cold.

Jonathan Kent’s production of Emperor and Galilean is another matter entirely. Ibsen’s 1864 drama is undoubtedly flawed, with excessive geographical gallivanting included at the expense of proper exploration of the play’s philosophical and theoretical arguments. But Ben Power’s adaptation has wrestled Ibsen’s hugely long original down to a more manageable three hours 20 minutes and offers some really thrilling moments.

In addition, the epic scale of the drama means that Kent and his team have had something wonderful to work with; the result is a spectacle grand enough to allow us to overlook the play’s flaws. The show will certainly be a particular delight for fans of Ibsen’s work, but even for those who've never heard of Hedda Gabler or A Doll’s House, Emperor and Galilean is a play worth discovering.

Another ‘lost’ play I saw recently was Wife to James Whelan, which received its British premiere at the New Diorama this April after being rejected by the Abbey Theatre, Dublin in 1936. Its writer, Teresa Deevy, doesn’t have the clout of Williams or Ibsen, but for a few years prior to her fall into obscurity with the rejection of this piece, she enjoyed real success. This neatly written drama is therefore worthy of staging for reasons other than the plays discussed above: it is a genuinely good play by a talented writer who was cut off in her prime.

So, should ‘lost’ plays stay ‘lost’? Not necessarily, but that doesn't mean that every drama that's fallen out of favour or never seen the light of day is worth dusting off; there's far too much good new writing waiting to be produced for theatre-makers to spend time digging for forgotten gems that might just turn out not to be gems at all.