Krank did a least portals run of Portal, with 22 portals used. Segmented “when I wanted to”, with no scripts used. He thinks 21 is possible, but he’s not that guy.
http://m.youtube.com/index?desktop_uri=%2F&gl=US#/watch?feature=m-feedu&v=9N56HjZrFig
I like that !
I’ve had another look and it seems like someone could shave another 2 portals off this. So 20 might be possible if you have an insane amount of time/luck and you can ABH like a god.
Check and check.
Nope and nope. (Me, that is.)
But I can still confirm that 21 portals can be done.
Chambers 11 & 12 (testchmb_a_07) with only 3 portals: