Those migrant who are in the United Kingdom, can apply to switch into this category if they have been in the following categories:

• highly skilled worker (tier 1);
• sponsored skilled worker (tier 2);
• student;
• student nurse, but only if your certificate of sponsorship shows that you are being sponsored to work as a nurse, doctor, or dentist;
• student re-sitting an examination;
• person writing up a thesis;
• overseas qualified nurse or midwife;
• postgraduate doctor or dentist, but only if your certificate of sponsorship shows that you have been sponsored to work as a nurse, doctor or dentist;
• student union sabbatical officer;
• qualifying work permit holder;
• Highly Skilled Migrant;
• a participant in the International Graduate Scheme (formerly known as the Science and Engineering Graduate Scheme);
• a representative of an overseas newspaper, news agency or broadcasting organisation;
  a participant in Fresh Talent: Working in Scotland Scheme;
• minister of religion, missionary or member of a religious order;
• member of the operational ground staff of an overseas-owned airline;
• innovator;
• a Jewish agency employee.

If you are not in any of these categories, you must leave the United Kingdom and apply as a new application at your local entry clearance post.