[O   III]  vs. total radio luminosity at 178 MHz (in units of    erg   s^-1 and    erg   s^-1   Hz^-1 respectively) for the 3CR sources with z < 0.3 (limiting for clarity to its bright luminosity end). HEG are marked with circles, LEG with squares. The green asterisks are ELEG, i.e. the relic RG. The triangles are objects that could not be classified spectroscopically. The dotted lines are the best-fit linear relation between L _[OIII]  and L₁₇₈ obtained for HEG and LEG separately.