protected function getRelationColumnValue($columnName, $record)
    {
        list($relationName, $relationColumnName) = getRelationDetails($columnName);

        if ($methodName = $this->customisesColumnValue($relationName.'_'.$relationColumnName)) {
            return $record->$methodName();
        }

        if ($record->$relationName) {
            return $record->$relationName->$relationColumnName;
        }

        return 'N/A';
    }