What happens to a town when the UK's most talked about artist leaves an unannounced drawing on a garage wall?

Season's Greetings, by the anonymous artist Banksy, appeared in Port Talbot in December 2018, days before Christmas, prompting a rush of visitors to swell the back lanes where the commentary on the town's famous steel industry now resided.

The drawing, across two walls at right angles, showed a boy playing joyously in a downfall of snow – but turn the corner and the viewer sees the "snow" is actually ash falling from a fire burning in a bin, echoing the larger plumes of smoke emitted day and night at the steelworks.

Now that event – and the wider story of the town's fate – has been turned into a play, Port Talbot Gotta Banksy, based entirely on transcripts of the townsfolk's response.

Tracy Harris and Paul Jenkins, south Wales-based playwrights, had worked together on a previous project using the same technique of verbatim speech, that time gathered from young people they were devising a show with, and were looking for ideas for another.

When they heard about the Banksy and went to visit, a chance conversation with a fellow director who said "someone should write a play about this" gave Paul "one of those lightbulb moments," that the material might be right under their noses.

However neither anticipated that what began as a plan to capture the response to a singular event would grow into a six-year labour of love documenting the end of a 100-year way of life for a working-class community.