a) the great way the BBC announced it (sound needed, but you’ll get annoyed after about a minute)
b) the Sci-Fi channel turned down the chance last year because they watched a few episodes and “found the series somewhat lacking and didn’t think it would fit into the network’s schedule”
I’m guessing the change of mind came about since there was a definite pick-up in story quality in the second half of last year’s season, because it’s now a success and because David Tennant is due very soon. Plus how many rubbish B-movies can you fill a schedule with before you start to put off your educated 30+ demographic? Anyone for Mansquito 2? Thought not. Better get some decent shows in instead then, hadn’t you Sci-Fi?