 Because of the varying technical and logistical demands of the 13  episodes of the first season, filming was broken into five  production blocks. Episodes 1, 4 and 5 formed block one, and was  filmed between July and September 2004. Block 2 comprised episodes 2  and 3, and was filmed between September and October 2004. Block 3  contained episodes 6 and 8 filmed between October and December.  Block 4 was split into two sub blocks, 4A and 4B due to the large  visual effects demands of episode 7 which on its own became block  4A, filmed between December 2004 and January 2005. Episodes 9 and 10  made up Block 4B, filmed from December through February 2005.  Episodes 11