At the end of Episode #2.6, Tommy Shelby is knelt by a grave dug out in a field, awaiting his assassination by three men. This is until one of the assassins shoots the other two instead, blowing massive holes in their heads. In the recap of the same scene in the beginning of the next episode, (Episode #3.1) everything is identical except the gaping holes in the heads of the two dead assassins have disappeared.
When Arthur gets up from the Wedding meal table to go and call Thomas, his jacket is on the back of his chair. When he finds Thomas, he is wearing his jacket.
The shot of Tommy in the grave shows his vest is not buttoned properly.
In Series 3, actors Jan Bijvoet and Gaite Jansen both play characters with a Georgian background. Being from Belgium and the Netherlands, both actors speak Dutch as their main language, which can be heard if you pay close attention to their played Russian accents.
In this series, Tommy drives a 1928 Bentley, four years after 1924 when the episode is set.
Boom mic visible for split second at top center of frame during tommy's dialog: "and now according to tradition..."