When, where and how is *_rg_lead['id'] available?

I need to get the id of the lead row before displaying the confirmation on the screen. I have tried a number of methods, but never get the id of the newly created row; $entry['id'] displays the form id of the form we're completing instead of the entry id, which someone would presume you would get from a field with the name $entry['id']. Searching documentation is hopeless because there are hundreds of results with "id" in it.