Playing Hippolytus, in Jonathan Kent's current production of Phedre, he beautifully signals the insecure, stiff-jawed heroics of a high-minded youth confronted by the desperate incestuous passion of his stepmother.
A matriarch continues to spell trouble for him in the same director's excellent modern-dress staging of Racine's Britannicus, an artfully chosen companion piece which joins Phedre in rep at the Albery.
This time Stephens plays the young emperor Nero, six months into a virtuous reign that will shortly turn into a bloody tyranny.
He owes his eminence entirely to his mother Agrippina who has committed all manner of crimes to put him on the throne, even to the extent of inducing her dying second husband to disinherit his own son, Britannicus, in favour of hers.
But Nero is beginning to grow restive at his mother's power-mad hold over him and he has fallen in love with Julia, who was intended for Britannicus. In revenge for his coolness Agrippina determines to join forces with the rival she wants ousted for his sake.
From his first bustling entrance, nervously shooting his cuffs and attended by some brutal-looking guards, Stephens's emperor is a wonderfully sinister/pathetic mix of arrestedness and assertiveness.
Through the clenched, almost Cowardesque delivery and the stiff, would- be imperious pose, you keep catching glimpses of a sulky, unsure little boy who looks as if he expects to be rebuked.
References to his mother's power send him into paroxisms of near-violence; it's significant, though, that while his hands hover hungrily over Joanna Roth's Julia, something inhibits them from actually touching her.
The effect of the performance is uneasily mirth-provoking and this is right because it brings home the dangerous indignity of Nero's position.
All tortured war-clawing guilt as the eponymous step-mother in Phedre, Diana Rigg here presents a lethally sophisticated Agrippina whose lofty derisiveness and arrogance remind you that this actress is a supreme mistress of high-comedy.
The long private session with her son reduces him to apparent tearful submission and Rigg's switch back to smiling cuddling possessiveness excites audience laughter in its brazen speed and totality.
But the laughter quickly dies because her assurance is quite unfounded, and, in the end, proves fatal for Kevin McKidd's duped and distraught Britannicus.
There's a beautifully sardonic edge to Jonathan Kent's fine production. Pairing this play with Phedre is a smart and thought-provoking move, producing a season that could be collectively entitled, with apologies, to the famous sitcom,Some Sons Do 'Ave 'Em.