We did this tour with Campbell. We met at 10am and got back around 4.30 so you do need to put aside a whole day. We thought we were well prepared for visiting Sachsenhausen but Campbell was able to put the whole experience into context. We learnt far more than we imagined and found the whole experience so worthwhile. We had considered doing this as a self directed tour but we were very glad of having a tour leader to guide us through. We highly recommend Mosaic as all their profits go to Amnisty International.