A reader in Portsmouth writes to ask the definitions of the various grades of motoring events. Briefly, according to the R.A.C. Year Book, they are as follows: Closed: events confined to members of the organising or joint organising clubs. Restricted: events confined to those clubs who have accepted the invitation of the organising club but, except in special circumstances, the number of clubs participating is limited to 10. National British: events open to any holder of a competition licence issued by the R.A.C. valid for the event. National Open: events open to any holder of an unrestricted competition licence issued by any national automobile club under the F.I.A. International: events open to any holder of an unrestricted competition licence under the authority of the F.I.A.