Éste es un médico plenamente cualificado, pero que no trabaja en asociación con otro médico en una consulta.

"A GP Non-Principal is a fully qualified GP who isn't, to all intents and purposes, a partner in a practice. Every person in the UK is entitled to register with a GP, and these GPs whom you can register with are usually called GP Principals.

But if they're off on holiday, or somewhere studying to improve the wonderful care they give, or are poorly (yes, GPs do get ill too), or are just really busy, then they'll often employ a GP to either cover their absence (a locum) or to help them in addition to their normal care (assistants and retainers)."
http://www.nanp.org.uk/patients.htm

"nanp" = "national association of non-principals"

HTH,

Andy