In the admin interface of Magento I need to modify the tables in the Sales / Order / View order so that it shows, besides the products name, their manufacturer as well.

I'm trying to look for the file to modify to make that happen. I thought I would find a section with all the columns that are displayed in app/code/core/Mage/Sales/Block/Order/Item/Renderer/Default.php but by inspecting it there seem to be no reference to the columns/product attributes.

I also tried to modify app/design/adminhtml/default/default/template/sales/order/view/items/renderer/default.phtml by changing

<?php echo $this->getColumnHtml($_item, 'name') ?>

into

<?php echo $this->getColumnHtml($_item, 'manufacturer') ?>

but it changed nothing, so I suppose that file is not involved...

Can anybody please point me to the right file to modify?

Thank you!