Gillian Slovo's incendiary play points a finger at the bureaucrats at the heart of the tragedy The shadow of Grenfell Tower has already produced Nick Kent and Richard Norton-Taylor's dispassionately forensic but devastating documentary plays based on transcripts from the Grenfell Inquiry. Now comes a companion piece, the National's Grenfell, a verbatim play using excerpts form the same source, but larded by Gillian S…