Nicola Sturgeon is set to announce the latest update on Scotland's five-tier coronavirus lockdown system today.The First Minister will make a speech to parliament on Tuesday afternoon - with millions likely to be placed under the toughest restrictions.She yesterday warned that areas of the western central belt could be moved to level 4 after cases have remained at a "stubbornly high level".In leaked documents, up to twelve local authority areas could be plunged under stricter lockdown measures