oh and an interesting interview with Gareth shortly after filming the second season he has this to say on http://www.garethdavid-lloyd.co.uk/qa.html

"Q: Do you think Ianto wanted Jack from the start in Torchwood?
A: If he did, he didn't know it himself. Maybe the sense of something was always there, but it took some time for it to become clear in his mind. There's stuff in Episode Twelve of Season Two that gives a hint."