A few people have contacted us, alerting us to the video (below) of someone completing Portal in 18 minutes and 5 seconds. Blimey.
Poster Maciej "groobo" Maselewski (see more of his speed runs here) believes he could get it under 18 minutes. He explains,
"Timing starts when you wake up in your cell, ends when you destroy glados's last orb, minus loading times. Also sorry for the bad aiming/positioning at the escape levels, I always get super nervous when I get to that part."
Part two if you'll only click on the following: