I never did finish doing my timeline comparisons, darn it, but I can tell you that for certain, I.D. was not the first in Series 4 according to timeline.
It has a start date of 6Feb11, and of the other three that I checked for series 4, Denial and Shaken come before I.D. in the timeline, and Duty of Care comes after. I'll find my AVIs tomorrow and check on the timeline for Help. I would be surprised if Help came before Denial in the timeline (which would make it the first episode in Series 4 by timeline) because there's only two weeks between the start of the last episode of Series 3 and the start of Denial. There's room, but only barely (1 week between is the shortest gap in the timeline, as I recall).