It has often been suggested that were it not for Lady Macbeth’s malign influence Macbeth never would have killed Duncan. She takes the superior position and through sheer force of will, that impels him to the deed.

Following Duncan’s murder Macbeth is tormented by his guilty conscious. He becomes paranoid and delusional. In Macbeth’s tormented mental state Banquo’s actions appear highly suspicious. He is sure Banquo will suddenly strike out against him. His only option is to murder him.

Even at the play’s close, Macbeth never totally loses our sympathy. There remains something sublime in his defiance. No soul to whom evil was congenial be capable of that heart-sickness which overcomes him when he thinks of the 'honour, love, obedience, troops of friends' which 'he must not look to have'.