Because I wasn't paying attention to which twitter account I was using on my phone. It was NSC's and not the one of the company I'm doing some freelancing for! It wasn't the first time, it won't be the last!
Edit: but thanks for the idea the next time I have an inside scoop!
I think that's a little bit unfair. The NSC twitter account, ie me, rarely interacts with Andy's stuff on twitter. I have no way of quantifying that, but I'd guess at that being 3 or 4 times a year, tops, and isn't done mockingly. The main reason for that is most days I don't even look at...