Doctor Who, given it’s very, very long history, is built, sometimes accidentally, more often on purpose, on it’s own internal traditions. Daleks appearing at the end of episode 1 in a classic serial, the first story for any new Doctor being unrepresentative of the era, that sort of thing.
In nu-Who there’s also a hidden tradition, that being the ‘Doctor-light’ story. Now in the sixties, when Season episode counts averaged in the 30’s or above, it wasn’t unusual at all for the Doctor or a companion to go missing either by unconsciousness or, as often, incarceration, for an episode or two. Near continuous production required that the actors get a week off and the stories needed to accommodate this.
In nu-Who when 13 episodes a year was still a bit over the average for a top drawer British production, similar considerations apparently applied. The real question regarding a ‘Doctor-light’ story, is whether the production team can get away with it, parcelling out just enough of the Tardis team so that the ‘double-banking’ can spread the budget just that little bit further. We might write about how successful this has been through the years a bit later.
As it was we feel Lucky Day did, quite well we thought, get away with it. It helps to have an ‘extra’ companion in Ruby to re-weave into the action, not to mention that Millie Gibson held 73 Yards together last year. Best of all, we didn’t see the betrayal coming. A genuine surprise.