The FT's chief UK commentator Robert Shrimsley and deputy opinion editor Miranda Green look at what Prime Minister Boris Johnson can do to keep Scotland and Northern Ireland in the United Kingdom. See if you get the FT for free as a student (http://ft.com/schoolsarefree) or start a £1 trial: https://subs.ft.com/spa3_trial?segmentId=3d4ba81b-96bb-cef0-9ece-29efd6ef2132. ► Check out our Community tab for more stories on the economy. ► Listen to our podcasts: https://www.ft.com/podcasts ► Follow us on Instagram: https://www.instagram.com/financialtimes'