Just thought I would share a run interval / speed set I do, along with my guys, generally in their race specific phase, 3-4 weeks out from their 'A' event. The key thing I want to see out of this one is not pure speed, but to see how consistent they can get the time on each interval. Perfect if you can do this on a track, otherwise a nice flat consistent ground is just as good. Total set is 10km, however the reps can be reduced or increased according to 'A' race distance.
Warm up - 2km and include drills of choice. If on the track, do the drills down the straights and jog the curves.
Main set - 4 x 400m at stand alone 10km pace with 300m easy jog / walk recoveries. 4 x 300m at stand alone 5km pace with 200m easy jog / walk recoveries. 4 x 200m at stand alone 3km pace with easy jog / walk recoveries.
Cool down - 2km easy
Try to do the efforts without looking at a watch and go purely on feel. This set will also help you get a feel for pacing yourself come race day.