Theatrical marathons are all the rage at the moment: while the New York company Elevator Repair Service have brought Gatz, their all-day theatricalisation of The Great Gatsby, to the West End and the RSC is in residence at the Roundhouse with its triple bill of Shakespeare’s shipwreck plays, the great peripatetic Irish company Druid has put down roots with a trilogy about what trying to find one’s roots means.

It’s part of the irony of the journey of these productions that not only are they themselves going to travel a long one from Galway to New York by way of London and beyond, but that they should have sought validation far from home by officially opening them at Hampstead Theatre. That meant that the Irish press flew over to attend the opening alongside their English counterparts (even if those of us on our home territory were in fact surprisingly under-represented). It also meant the impressive attendance of no less than the current president of Ireland, Michael D Higgins, for the entire day. This is an occasion, clearly, of national theatrical pride.

It is one that, moreover, pays specific tribute to one of Ireland’s native theatrical living giants; and like DruidSynge, the company’s previous cycle of plays by JM Synge, DruidMurphy presents a rare opportunity to survey a span of one writer’s works, namely Tom Murphy, including two plays from the 1960s and another from the 1980s. They share an overarching narrative of Irish emigration - from an enforced, desperate one in the final, bleak play Famine, when the potato blight means that the offer of an uncertain future in Canada is made to the inhabitants of one starving community; to a story of four brothers settling in 1960s Coventry in A Whistle in the Dark. Conversations on a Homecoming sees a return to Ireland after a decade away of a man who has been trying to make his way as an actor in 1970s New York.

Though the plays were conceived as separate entities, not as a trilogy, the boldness and brilliance of Druid’s cross-cast production grants them a stylistic unity, staged inside the same frame of corrugated iron sheeted walls but distinctly designed environments by Francis O’Connor that stretch from a pub and lounge to crop fields.

Yet the plays couldn’t be emotionally more different. Conversations on a Homecoming is an event of quiet but highly charged truth-telling, staged in unbroken real time, in a pub setting, riveting in its easy rhythms of people who know each other only too well but for whom confronting their personal legacies and disappointments, over endless pints, is harder.

A Whistle in the Dark comes at an altogether higher emotional pitch, which lays out a haunting story of a taunting father’s domination of his sons, still stirring them into open conflict with each other even now as adults, but takes no responsibility for the consequences.

Where those plays are each domestic in scale but intense in impact, Famine less successfully takes on a larger canvas to provide an overly dense history lesson. Garry Hynes, one of the great directors of Irish theatre, lends them each a poetic fluency, and they are played with an arresting integrity throughout. Amid a rich ensemble of 17 actors, Niall Buggy is particularly stunning as the fierce patriarch in A Whistle in the Dark, but there are no false notes anywhere in a cycle that can be seen in one long, but rewarding, day or separately.