"Everyone" is not a very helpful definition.
Best to look at the MHRA Super Moderators guidance three sections below. The FAQs and the MHRA GCP Guide (2012) give some advice:- "Training needs may range from a detailed knowledge of GCP principles and associated UK Regulations and European guidance to an awareness of particular GCP principles, and training can be tailored accordingly. If an activity is part of a person’s normal clinical role and all other protocol activities are undertaken by a member of the research team, then no GCP training may be required; however this should be reviewed as part of the risk assessment for a trial. The MHRA strongly recommends training in relevant aspects of GCP for anyone involved in conducting CTIMPs, even if the activities are part of an individual’s routine job (for example, tailored training in aspects such as documenting activities in source notes and recording adverse events). It is recommended that assessments of the scope or level of GCP training required by particular individuals or roles are documented."