In an early scene in Brian Friel’s breakthrough play Philadelphia, Here I Come! a young man imagines being aboard an airplane flying into the west over the Atlantic Ocean.

In this fantasised journey, the placid passenger aircraft becomes a gunner plane, swooping down to the fishing trawlers below. This daydream plays out in a house in Ballybeg, County Donegal, in the bedroom of Gareth (Gar) O’Donnell, the play’s lead character or protagonist – whom Friel quickly establishes as a thoughtful, witty and searching young man. An imaginative vision like Gar’s is a useful way for a playwright to go beyond the confines of the stage and escape the immediate setting of the play. In Friel’s inventive approach, the protagonist is split into two personas played by different actors: Gar Private, who gives voice to the protagonist’s internal monologue; and Gar Public, his external face.

The central dramatic device of Philadelphia, with two actors playing the protagonist on stage – of whom only Public is seen and heard by the other characters in the play – gives Friel a special freedom to reflect on the dilemmas of migration.

This was a vexing matter for young people and their families in 1960s Ireland, and through Gar Private’s thinking aloud, Friel contemplates how the ties that bind a person to the place where they have grown up might be frayed or broken altogether. Where Gar Public is reticent and unsure of himself, Gar Private is forthright, frank and mischievous in sharing his thoughts. He doesn’t hesitate to harangue his upright father – county councillor and shopkeeper S.B. O’Donnell – even if the audience knows that Private’s target is oblivious to his cutting wordplay. He teases and goads most of the other characters around him, too: he questions the motives of his friends, finding flaws in their ordinary, parochial lives; equally, he pokes fun at his brassy American relatives who are back for a visit to the home country.