This page explains the circumstances in which you can apply for permission to stay here as the dependant of the entrepreneur category (Tier 1 Entrepreneur) without having to leave the United Kingdom and apply for entry clearance.
You can apply for permission to stay here as the dependant of a entrepreneur without having to leave the United Kingdom and apply for entry clearance if your last grant of entry clearance or permission to be here was as the partner or child of a person who has, or is at the same time being granted, leave to enter/remain as a Tier 1 (Entrepreneur) migrant.