Historical aspects great and ex-prisioner talk fantastic. Using a personal guide, apart from transporting us there and accompanying us on the trip, unfortunately there wasn't much else that the guide could have done as once on the Island, the 'official' guides free did everything else. So really, one can make one's way there and back via the ferry with no need for paying for a guide.
You have to go to Robben Island if in Cape Town. Tour conducted by ex-prisoners, very informative and sometimes moving to see what the Government did to people who disagreed with them. Wanted more time in the prison than the tour allowed, but understandable because it is very busy.
This is a must but because of the way it is organised tour companies lose control once you are on the boat and then at Robben's Island it is severely disorganised. Or at least it was the day we went. A must do but be patient. Groups are a little too large for everyone to hear and see all at the same time