Bradley Manning is Welsh. That was the spark that led Tim Price to write this pulsating play about the WikiLeaks whistleblower’s life for National Theatre Wales. That the infamous 25-year-old was, not long ago, a teenager in Haverfordwest, shapes the whole narrative: Manning is presented as the latest in a line of Welsh radicals, the heir to Aneurin Bevan, Dic Penderyn and the Rebecca Rioters.

The show begins with an immersive trail around the deserted school venue, to an unnerving soundtrack culminating in a mix of the audio track from the leaked ‘Collateral Murder’ video of a US helicopter shooting at Iraqi civilians. Soldiers stare out from otherwise empty classrooms, setting the tone for some thoughtful experimentation with the idea of occupied space both in the physical world (Iraq) and online (hacking), and the potential of each for fostering radicalism.

Performances are streamed online with social media debates encouraged, which does a lot to highlight the strength of biographical theatre over blockbuster biopic: the show has evolved to include updates from Manning’s trial as it happens, while the internet responds to the performance in real time.

A slick ensemble cast shunts us forwards and backwards in Manning’s life. From his imagined school days to his unhappy army career and eventual incarceration, we get to know a boy, small for his age but hot-headed and good with computers, who is given this choice by his father: ‘Do you want to be a man and join the army, or do you want to be gay and work at Starbucks?’

The play is a powerful argument about radicalism, technology and personal battles, framed in a gripping study of the character of a complicated modern anti-hero.

Pleasance At St Thomas of Aquin’s High School, 226 0000, until 25 Aug, 7.30pm (Sat & Sun 2.30pm & 7.30pm), £12 (£10).