Breaking a race down into 3 parts

I recently purchased Sarah Rowell's book 'Off Road Running' which offers advice on every discipline of Off Road Running, one section being on Cross Country. As I am currently in the middle of the Cross Country season, I decided to try one of the specialist sessions she suggests.
Using various means of science, Sarah explains to be a good Cross Country runner 'your body has to be able to cope with an initial increase in circulating blood lactate, one that can then be dissipated (recovery) while still running at a sustained racing pace, before repeating the process of running fast at the end of the race when you are tired.' What better way to practice than in training? None says Sarah, 'one of the best ways of preparing for this is to replicate it in training, for example: 3 mins fast, 1 min recovery, 10 to 15 min sustained, 1 min recovery, 2 mins flat out.' Obviously in a race you wouldn't get the 1 minute recovery between the fast 3 minutes at the start and the 15 minutes sustained running and again before final fast 2 minutes. It is however as close as you are going to get to recreating race conditions in training as I found out today!
I did 2 sets of the above with the first set containing 15 minutes of sustained running and the second one containing a little less, 12 and a half minutes. So splitting the race (or training session but it felt like a race) into three parts: NOTE TIMES ARE PACE PER MILE.
Fast 3 minutes (similar to start of race) : 5:30
Sustained 15 minutes (Middle stage) : 6:11
Flat out 2 minutes ( End of race) : 5:29

I did a recovery of 7 and a half minutes before the second set.
Fast 3 minutes (similar to start of race) :5:52
Sustained 12 mins 30 seconds (middle stage) :6:14
Flat out 2 minutes (End of race) :5:29

Looking at the times, the start of the second 'race' was clearly a little slow but the Garmin was playing up a little at that time so I would say the pace was nearer to 5:40. I clearly had something left in the tank on the second as I reproduced my finish from the first effort.
This was a really tough session, possibly the hardest I have ever done. Other than after a hard race, I don't think I have ever been as tired as this (I was on the floor which only usually happens after a race). Sessions like this are what will make the body stronger come race day so I will certainly do this more often from now on. I rounded it all off with a 10 minute warm down, bringing the day's running total to 7.5 miles (most of which was on a very flat cricket pitch like field). A great session which produced some pleasing results. Roll on Tuesday for the next one!