public function &GetActiveShippingGroup()
    {
        if (is_null($this->oActiveShippingGroup)) {
            // fetch the one from the shop
            $oShopConfig = TdbShop::GetInstance();
            $oActiveShippingGroup = $oShopConfig->GetFieldShopShippingGroup();
            if (false == $this->SetActiveShippingGroup($oActiveShippingGroup)) {
                // unable to set - group not in allowed list
                $oList = $this->GetAvailableShippingGroups();
                $oList->GoToStart();
                if ($oList->Length() > 0) {
                    $oActiveShippingGroup = $oList->Current();
                    $this->SetActiveShippingGroup($oActiveShippingGroup);
                }
            }
        }

        return $this->oActiveShippingGroup;
    }