I started re-watching the series because after reading about the new season, old plot lines re-surface in the current season.
It's amazing how many things and people I've forgotten.
They have really done a good job progressing the characters and story as the seasons unfold.
Yes, things are really coming full circle now in Series 6, with harking back to many of the characters we met in Series 1.
Me thinks this is not just a plot device to let us see Mercurio's macro take on corruption from top to bottom and inside out, but a thinly veiled "conspiracy" of his own and the BBC's to get folks to find series 1 to 5 and watch them all OVER again on the sub services! haha