In a blistering one-off show, poet Lemn Sissay heard " for the first time " the record of his suffering as a child in care. He explains why the theatre was the safest place to relive his beatings and betrayal I have never been in a theatre audience like this one " so loving, supportive, involved. Then again, there has probably never been a production quite like this. It is the ultimate verbatim theatre. What's more, …