First of all, I must thank Jay66UK, and the numerous other posters who warned about the W6R1. Bearing their warning, I did took the run seriously.
Having finished the run, I can now say that I know why W6R1 is tricky, it is in fact, the quite opposite of W5R3. Before attempting W5R3, you are afraid that you wont be able to run for 20 mins, but before W6R1, you feel confident that you will be able to complete that with ease, and that can lead you to false security.
In W6R1, even though the runs are short but the cool down/ walking period is only three minutes, and the run-time is increased. As a result, if u relax too much during the first 3 min cool down period, u will feel a proper sting in your legs during your second run, and that is the tricky part, cuz it can increase the mental pressure.
I guess W6R1 is added to the program to test the strength of coping with the shorter warm-up periods combined with longer runs. I mean, W6R1 does test and increase your physical and mental stamina.
Thanks to the warnings in advance, I completed the second run, the first half-way mark was difficult. In my third run, I ran for 10 mins instead of the required five because I was feeling pretty good and wanted to cover 5 KM.
All in all, a very good run. I will attempt it several times (for stamina and fun), then I will go to the W6R 2/3, which wont be hard at all.