Danny Cohen became Controller of BBC One in October 2010, having been the controller of BBC Three since 2007. He was the incumbent controller for the 2013 50th anniversary celebration.
In 2011, he famously said that Steven Moffat's commitments to Sherlock necessarily meant that Doctor Who's output would drop in 2012. Even though Moffat immediately used Twitter to push back against Cohen's statements, ultimately Cohen was proved correct.
There's only so many hours a day [Moffat] can be awake. The man has to sleep and eat, and he's got a family.Danny Cohen