Barrowman began his career on the London stage in Cole Porter's Anything Goes and was also featured in the 2004 Porter biopic Delovely doing a duet of Night and Day with Kevin Kline. (a sample here) Captain Jack's most recent album is all Cole Porter numbers.
No shock that Barrowman admires Porter, he was a master of innuendos with lyrics like, " I'd like to sup with my baby tonight, Fulfill the cup with my baby tonight, But I ain't up to my baby tonight, 'Cause it's too darn hot!"
PS - Advance reports are that in tomorrow's new issue of Doctor Who Magazine Russell T Davies will talk a bit more about Torchwood, including that he has never approached Charlotte Church to be in it. Check back for more as it breaks.