PageTable: How to reference "parent" page?

[MadeMyDay]

Struggling on a problem with the new PageTable field. If the field is set to a custom page holding the entries, I don't know how to define the original page where the PageTable field is included.

Say I have a page with id 1040 and my entries are stored under a page with id 1020:

If I render $page->parent->id, I always get 1020 (of course). How can I access the id where the PageTable field is originally included (here: 1040)?

[Soma]

There's no reference, it's a normal page. The only reference is the pagetable field itself. Ring a bell?

$thepage = $pages->get("template=basic-page, mypagetable=$page");

[MadeMyDay]

Soma, thank you. As always: Easier than I even dreamed of.