public function mark_inprogress($timestarted = null) {

        $timenow = time();

        // Set reaggregate flag
        $this->reaggregate = $timenow;

        if (!$this->timestarted) {

            if (!$timestarted) {
                $timestarted = $timenow;
            }

            $this->timestarted = $timestarted;
        }

        return $this->_save();
    }