As Three Line Whip points out, the Tory MP David Heathcoat Amory may have made things a little clearer. Here's what he told The House Magazine:
"The next Conservative government will renegotiate our relationship with Europe and finally the people will have a vote on this."
A party spokesman has already batted down expectations, with a coy "We'll go into more detail when the time is right". But it's an encouraging sign nonetheless.