There are no set requirements, but you'll find it useful to have experience in customer service at a supervisory level, and some experience of bar work.
You'll usually need to do the Pre-Entry Awareness Training e-learning course. You'll also need to complete the British Institute of Innkeeping Awarding Body Level 2 Award for Personal Licence Holders to apply for a Personal Licence.
It's possible for anybody with enough financial backing to buy a pub or bar.
As a manager of a pub or bar that sells food, you'll usually need a qualification in food safety accredited by the Chartered Institute of Environmental Health.