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"PBS exec Rebecca Eaton has insisted that Sherlock will always be comprised of three-part series. Three 90-minute instalments of the Benedict Cumberbatch detective drama aired in 2010, with three more debuting in January 2012 in the UK.   &amp;quot;[The format is] very closely held,&amp;quot; Eaton told Collider. &amp;quot;Steven [Moffat] crafts them, and Mark [Gatiss] writes some of them. It&amp;#039;s a lot of work, and [Steven] also does Doctor Who and he worked on Tintin, so there couldn&amp;#039;t be more than three.&amp;quot; Eaton argued that Sherlock co-creators Moffat and Gatiss use up all of their &amp;quot;creative juice&amp;quot; on the show. &amp;quot;I think there will only ever be three at a time, if we&amp;#039;re lucky,&amp;quot; she said. &amp;quot;It&amp;#039;s getting harder and harder to do another season, not just because Benedict and Martin [Freeman] are getting such high profiles, but Steven and Mark are busy and in demand.&amp;quot; Eaton also claimed that she was not surprised by the success of Sherlock in the US. &amp;quot;I knew, as soon as I saw Sherlock, that it was going to be special,&amp;quot; she explained. &amp;quot;The fact that it caught fire the way that it did, didn&amp;#039;t surprise me.&amp;quot; The second series of Sherlock premieres on Sunday, May 6 on PBS. A third series is also in development, with filming expected to begin in early 2013. "^^<http://www.w3.org/2001/XMLSchema#string>
<http://www.digitalspy.com/tv/sherlock/news/a379411/sherlock-no-more-than-three-episodes-a-year-says-pbs-exec/>