Y Sŵn: this dramatisation of the struggle for S4C is worth tuning into

Outside of Wales, it might be a surprise to learn that Welsh rebellion against Margaret Thatcher’s government began not amid the coal beneath the mountains of the country, but in the airwaves above them. Y Sŵn tells the story of the battle for a television channel solely in Cymraeg, something the Tories had promised in their 1979 election manifesto but reneged on when Thatcher swept to power later that year.

Central to the struggle was Gwynfor Evans, played here with quiet passion by Rhodri Evan. In 1979 Gwynfor was leader of Plaid Cymru but was also a casualty of the general election, losing his seat. Having also suffered a resounding defeat in the separate 1979 referendum on Welsh devolution, he is pictured struggling with dark thoughts, peeling potatoes with a sharp knife or fantasising about walking into a lake and not coming back. The real Gwynfor did indeed consider ending his life in a symbolic act of patriotic martyrdom, hoping his death would inspire a movement.

But the simple prospect of a television channel, as powerful a symbol (and medium) as a nation could seek, offers the toppled politician another course. Dissatisfied with the direct action of legendary folk singer Meredydd Evans, who broke into the Pencarreg television transmitter with two fellow academics, Gwynfor instead elects to go on a hunger strike. Doing so creates tension at home and charts a collision course with the Welsh Secretary Nicholas Edwards, the Home Secretary Willie Whitelaw, and of course Margaret Thatcher herself.

Produced by S4C , seemingly conscious of which party is currently holding the purse strings, Y Sŵn is careful in its portrayal of government figures. There are no gnashing caricatures here, no wilful nastiness, only a sort of stubborn bemusement that despite having won a national election, not everything is going their way. Gwynfor, meanwhile, is steadfast in his earnest conviction, which is why he is taken so seriously before the fast even begins. To underline the issue, writer Roger Williams and director Lee Haven Jones have Gwynfor watched over at times by the figures of Mahatma Gandhi and Martin Luther King, Jr. These two fellow pacifists are literally in conversation with Gwynfor through historically accurate quotes, bolstering his determination for radical peaceful protest and ultimately for potential martyrdom.

This device may seem over the top, but it appears in the context of a film that is not afraid to experiment. Scenes in the Home Office are filmed in a widescreen aspect ratio and stark black and white, while scenes in Wales are in vibrant colour and boxy 4:3. This is particularly effective when Thatcher herself is on a visit to the Rio Tinto aluminium smelter in Anglesey: as she rides in her car talking with an aide, the scene is wide and monochrome, snapping abruptly to square colour as the car is mobbed by protestors shouting in Cymraeg and calling Gwynfor’s name.

Similarly, large colour captions pop up over the action to emphasise key language. The screen flickers and jerks at moments, stuttering and whiting out like badly played celluloid. The dialogue is peppered with cuts that illustrate the topic, whether they be stills of the Welsh mountains when one lobbyist is complaining about the difficulties of broadcasting on such terrain, or archival footage of politics and protest. Rather than undermine the seriousness of its subject, these techniques lend the film a playful punkish quality (underscored by an excellent soundtrack that includes the likes of Elfyn Presli’s ‘Jackboots Maggie Thatcher’ and, naturally, Catatonia’s ‘International Velvet’), belying the fact that this is a film whose principal actions take place either in the offices of ministers and civil servants or at an aging politician’s dining table.

This playfulness is pushed to the point by the final scene, which – in a nifty formal device I won’t spoil here – collapses 40 years of history and leaves us staring into the eyes of Lily Beau, the actress who plays Ceri Samuel, a vital character who, as a member of the civil service in the Welsh Office, is able to offer insight and a sympathetic presence for the audience amid the bureaucratic halls of power in Cardiff and Westminster. A singer-songwriter and young woman of colour, Lily Beau also offers a glimpse at the representation that is as vital to the present and future of Welsh culture as Gwynfor Evans is to its past.

► Y Sŵn is in Welsh cinemas from now until 24 March; there are also screenings at the Finsbury Park Picturehouse (13 March), FACT Liverpool (20 March), Storyhouse Cinema, Chester (23 March) and HOME , Manchester (3 April). The film will be available to watch on BBC iPlayer later in the year.