Rumour has it that the episode will centre around the famous Battle of Hastings where King Harold lost out to the Norman invaders, led by William the Conqueror. It seems that the cybermen have other plans and intend to ensure that Harold wins, causing the English language as we know it to cease to exist and thus causing cosmic havoc across the timelines as a result. In order to do that, the cybermen infiltrate the Saxon army and we can look forward to seeing the Normans obliterated by their deadly ray guns.
OK, OK the above is all completely made up (even though there may be a story there for you, Mr Moffat!). The above picture was taken at Berkely Castle in Gloucestershire at a Medieval re-enactment. Come on though, we go you for a minute, didn't we?