You enter a dim, dirt-strewn trench. It's the middle of the First World War. A pair of British officers enthusiastically encourage you to sing Christmas carols. So begins the inventive, gripping first part of excellent double bill The Bunker at the Southwark Playhouse's new home, tucked in by a railway bridge halfway between Borough and Elephant & Castle.

The tight cast of four confront us with two adaptations, Arthurian legend Morgana and Greek tragedy Agamemnon, both set in the trenches. What's really clever in Jamie Wilke's script is how the action is both so vivid and yet all about the soldiers' state of mind.

In Morgana, three public school boys who all joined the war effort together grapple with the absence of their fellow knights of the round table. Compact, muscled Sam Donnelly bristles as Lancelot, real name Arnold, needling the naiver Gawain (James Marlow) to the annoyance of milder mannered Arthur (Dan Wood). Serena Manteghi as Morgana is the shapeshifter who represents all of the women dear to the men, whether it's Arthur's sweetheart Gwen or Gawain's mystical French amour.

Picking up the pace in the second half, Agamemnon starts with a bang as clouds of smoke cloak the trench. Marlow, northern accent underlining the different role, is the soldier in the title role seething with guilt for never sending his wife letters from the front line. We see his fears resolved in flesh in the middle of the bunker: quick Yorkshire lass Clytemnestra (Manteghi) becoming brittle with anger at home, finding solace with bumbling Aegisthus and plotting her revenge.

It's an accomplished, fresh show from company Jethro Compton Productions, (effectively a new, streamlined incarnation of immersive Edinburgh fringe darlings Belt Up) with four excellent, doubled up, turns from performers with stars in the ascendent.

Dark, psychological strains of war unmistakably pierce The Bunker: tightly directed, subtly produced, it gives new meaning to the stories we know so well and a stretch of history we should never forget.

- Vicky Ellis