Originally Posted by Aggro
Actually - from the film when Gordon went into the sewer and was captured by Bane's men, he read the speech Gordon wrote about Harvey Dent and Batman and worked out who was the Batman. This relates to the comics where Bane deduces who is the Batman in a matter of months.
Yes, that is a good theory but keep in mind that the characters and events in the trilogy do not exactly follow the comics.
I don't think Bane deduced Batman's secret identity from the text of Gordon's unread speech. Gordon, himself did not know who the Batman was until Batman made a reference to the incident in BB (not specifically referring to the scene for those who have not seen either BB or TDKR yet).
I don't think any of the characters realized BW was Batman merely because the Batman "went into hiding" and disappeared after Dent's death was blamed on him. Remember, BW becoming a recluse related to the death of his love and childhood friend, Rachel Dawes by the Joker and indirectly by the Batman by saving HD instead of her.
It is clear that Talia and Bane had at one time been in the LOS (in the Trilogy) before the death of Ra's al Ghul although Bane had been excommunicated at that time. Ra's al Ghul and his army knew Bruce Wayne was the Batman (see the scene in BB where Ra's al Ghul and some of his army attend Bruce's birthday party. Ra's al Ghul makes his presence known to Bruce by having an elderly guest announce him, makes his intention to destroy Gotham to Bruce known when he greets him and then burns down Wayne Manor), It stands to reason that Talia, Ra's al Ghul's daughter and his successor as the leader of the LOS knew Bruce was the Batman as well as Bane since they had a well-drawn plan to destroy Gotham and take their revenge on Bruce-Batman for killing Ra's al Ghul (which included forcing him to helplessly watch the slow destruction of Gotham on tv from the "unescapable" prison.)