Agamemnon, The Scoop, Riverside, London

In a happy conjunction, the free open-air season mounted by Phil Willmott and the Steam Industry at The Scoop, the amphitheatre next to City Hall on the south band of the Thames, includes Aeschylus' Agamemnon while the Lyttelton Theatre offers a provocatively topical revival of Iphigenia in Aulis. Euripides' play takes a caustic look at the warped psychology and murky motives of the men about to embark on a military invasion. What happens when the eponymous Greek king returns from war in Troy is the subject of the Agamemnon.

In a happy conjunction, the free open-air season mounted by Phil Willmott and the Steam Industry at The Scoop, the amphitheatre next to City Hall on the south band of the Thames, includes Aeschylus' Agamemnon while the Lyttelton Theatre offers a provocatively topical revival of Iphigenia in Aulis. Euripides' play takes a caustic look at the warped psychology and murky motives of the men about to embark on a military invasion. What happens when the eponymous Greek king returns from war in Troy is the subject of the Agamemnon.

In Willmott's sharp, modern-dress production, the man who was willing to barter his daughter Iphigenia's life to procure the winds needed by the Greek fleet arrives home as a conquering hero, only to discover that not everyone agrees that the end justifies the means.

The director has not set himself an easy task. The audience at this venue is diverse, ranging from serious theatre-lovers to wine-quaffing picnickers to people who have been drawn in by the spectacle. That's part of the charm of the event. Aeschylus' play, though, has a particularly involved and complex backstory and Willmott deserves credit for the way he has made this gripping and accessible to an eclectic crowd through re-enact- ments using model ships and characters in masks and a doll version of the sacrificed child.

With its machine-gun-wielding guards and its gung-ho returning soldiers who descend through the audience, the production conjures up a powerful atmosphere of the unease and moral muddle of a society where the old justifications are unravelling and where only a fool would imagine military victory can abolish festering resentments at a stroke. The careful stage-management of the amplified homecoming address by Stewart Alexander's slightly Americanised Agamemnon indi- cates an underlying discomfiture, an impression exacerbated when he repeatedly tries to cut short the interventions of his wife Clytemnestra (Olivia Macdonald) with premature, supposedly uxorious applause.

The Scoop's architecture is suited to Greek tragedy, its stone steps creating a creepy environment for the carpeted staircase up which Agamemnon walks to his offstage doom. With the fine Chorus imitating the thumping heartbeat and buzz-ing mental disarray of Kerry Skinner's vividly distraught Cassandra, there's a particularly charged intensity to the captive girl's preparations to follow the hero into what is, for her, a hideous and foreknown fate.

Willmott himself appears as Clytemnestra's lover, Aegisthus, whom he portrays as an arrogant toff oozing the kind of cowardice that would sit out a war and wait for a woman to perform his vengeance for him. At the end, this new dictator is seen pointing a machine-gun at the crowd while backing nervously into the palace. It's an image resonant with the unresolved. Recommended.

In rep, Thursday to Sunday, to 5 September