Speaking to Radio Times this afternoon news from Benedict Cumberbatch about series 4 (which isn't really news considering we heard series 3 will have a cliffhanger ending, but there you go.)
http://www.radiotimes.com/news/2013-03-12/benedict-cumberbatch-confirms-sherlock-series-4
"You are in for an absolute stonker. It's going to be a treat," said Cumberbatch,
"It's a terrific episode," added the star, speaking at the South Bank Show Awards,
http://www.radiotimes.com/news/2013-03-12/benedict-cumberbatch-on-the-return-of-sherlock-you-are-in-for-an-absolute-stonker
Series three begins filming next Monday, 18 March,
http://www.radiotimes.com/news/2013-03-12/benedict-cumberbatch-confirms-sherlock-series-4
"You are in for an absolute stonker. It's going to be a treat," said Cumberbatch,
"It's a terrific episode," added the star, speaking at the South Bank Show Awards,
http://www.radiotimes.com/news/2013-03-12/benedict-cumberbatch-on-the-return-of-sherlock-you-are-in-for-an-absolute-stonker
Series three begins filming next Monday, 18 March,