You have to be a member of the GTROC to be covered and it has to be an event organised under the Club's rules. i.e. if in a public place then full permission must be sought and granted. All GTROC members are covered at such events, non-members are not covered, even if it is a GTROC-organised event
It does not cover track days.
It is public liability insurance only and covers you in case you get sued, run over someone's dog, someone slips on oil you've left behind etc. In all other respects your car insurance will be sufficient.