This is exactly the type of story I tell when people are anti pair programming. I ask them if they’ve ever lost a days code (usually asking if they ever used source safe) and that when they finally knuckled down to write it again, it took about 20 minutes. As the writing the code wasn’t really the hard part or the bottleneck, solving the problem was the hard part. Hence pair programming having two heads on one problem to solve it better/faster, find the edge cases etc.

Out of curiosity, was it really fast for you to do it in that extra day or did it take all day?