Spot the Difference - Corrie's 50th cast photos

Judging by Corrie fan comments on twitter, we're not the only ones to have noticed a couple of cast members who look like they've been Photoshopped onto this Coronation Street 2010 cast photo. Look at the back row for Ben Price (Nick Tilsley) and Craig Charles (Lloyd Mullaney).  In Coronation Street's 50th anniversay official book, neither of them appear in the very same cast picture there. I wonder if they missed the photocall on the day?  Click on the picture to make it larger so you can see the two guys on the back row.