Inside is about young banged-up fathers, researched in Rochester Prison, developed at the National Youth Theatre, and now presented by Playing On in association with the Roundhouse (or the Round House, as we used to call it).
Most interestingly, in Osment's final script, the verbatim-sounding speeches and letters of the prisoners are incorporated in the outer scheme of a prison workshop itself, so that we see one of the play's directors, Jim Pope (the other is Osment) playing a version of himself as a creative catalyst on a two-week project, culminating in a performance for friends and relatives.
This was my first visit inside the new Roundhouse studio (the old one used to be a dark, dank cellar), and it provides a perfect arena for the prisoners who face the walls when isolated in their cells and then step onto the underlit stage for the rehearsal sessions, or the pool table, or the gym, looking for a chance to get off the wing.
There's the bolshie troublemaker, the abused young paedophile, the sullen murderer, the quick-witted drugs dealer -- all seven men are characterised beyond their stereotypes, and the richness of the writing comes in not only their interplay but their interaction with the workshop leader and his assistant -- whose gayness figures strongly in the truth-telling games.
But it's the confessional speeches about what these prisoners thought of their own fathers, and what they might hope for their own children, by way of trying to learn lessons and reform, that gives the show its emotional power.
What might have been a routine exercise in do-gooding social therapy becomes a genuine drama of rich texture and revelation. Hats off to Osment and Pope, both proteges of that fine director and teacher, Mike Alfreds, who founded Shared Experience and was in the audience last night.
Even though I live in the People's Republic of Camden, and a couple of stones' throws away from the Roundhouse, it's been difficult to get any sense of involvement or buzz about the place recently, except when hordes of drunken goths emerge from Chalk Farm tube station for an Alice Cooper concert.
It's over four years since local philanthropist Torquil Norman re-opened the expensively refurbished old Victorian railway shed and gin warehouse, and from a theatre point of view there's rarely anything one wants to go and see there.
Another RSC season might change that (the first, under Adrian Noble's watch, was a mixed success, with a ridiculous and expensive theatre module built within the stunning architecture; Michael Boyd's history plays fared better) -- and I don't really understand why the RSC doesn't count its losses and set up London shop permanently in the place.
In the meantime, genial executive director Marcus Davey bounced pleasantly up to Lyn Gardner and me last night to promise us that the re-designed bar and restaurant was going to be a great improvement.
It certainly looks to be very amenable, but it needs to take off as a destination facility rather like the Young Vic bar has done. Every time I go past the place there is absolutely no-one sitting in there.
Again, perhaps that will all change at the end of this month when the RSC hits town...the Alice Cooper goths have no need of a comfortable lounge bar hang-out; they are spoilt for choice in the scuzzy pub and edgy club department right outside and down to Camden Lock.