It was recently noted by an extra, known as Rimshot, working on the production that the show was preparing to film a three-episode production block. This has led to a good deal of confusion as to just what that means, but thankfully Adam Whitehead, U.K.-based book blogger, steps in to explain this over at the A Song of Ice and Fire Forum. Here’s the key paragraph:
“The block system sees several episodes combined into one solid block of filming and production lasting many weeks, maybe a month to two months. This block will involve the same behind-the-scenes personnel, and will be designed to maximise efficiency and minimize costs, so episodes set in the same location, using the same guest or recurring actors and so on will be combined, regardless of the actual transmission order of the episodes. Most notably, the same director will be assigned to the entire block. The block will be prepped, read-through, go through pre-production and budget meetings and then filmed and put through post in one long process. Usually whilst one block is filming, the next director will be stepping up and prepping the next block so the actors go from filming one block to the next (sometimes with a short break between them).”
Do check the rest of his post, as Adam compares to the more usual American network production method, and details how Doctor Who has used the production block method.