Forty years on from its first performance at the Hampstead Theatre and original screening on BBC1 soon after, Mike Leigh's Abigail's Party - telling of two marriages spectacularly unravelling at an awkward neighbourhood drinks party - remains a pinnacle of British theatre. Here is the original script, complete with a new introduction by Mike Leigh describing the play's unlikely genesis, how it came to be made and where he believes it fits within his oeuvre as one of the country's leading writers and directors.