Help, mail preview missing on macOS High sierra

macOS & Mac Apps

I now realise that since installing High Sierra I have lost my preview pane in Apple Mail. When on an email in say inbox I press VO and nothing happens. Before High Sierra VO j would jump to the preview window and VO j again would return to that particular email in the inbox. I have tried ticking the View Classic layout and unticking it with no effect. Does anyone have any ideas please?