That Summer is set in the late summer of 1984, at a time when miners were striking all over Britain as their unions and the Conservative government led by Margaret Thatcher, fought a battle that would change the industrial outlook of Britain forever.
In Edgar's play, a middle-class couple, Howard and Cressida, have decided to provide some support to the miners, by welcoming two girls from the mining community, daughters of striking miners, to join them in their holiday home near the Welsh coast. By placing these children of the working class amongst the interested, but unvested middle class, Edgar shows how an ideological battle can be fought not just intellectually, but experienced as a mere inexorable fact of life.
In a note on the play, Edgar writes 'That Summer is set against the background of the 1984-5 miners' strike. The play is a work of fiction and its characters are invented. But it nonetheless owes much to many Rhondda miners and their families'.
That Summer was first performed at the Hampstead Theatre in 1987.