Indeed there are a number of pub tours of historic areas of London and they do vary in standard

I have personally been on one which I can highly recommend and have posted more information below

For a source of good general information, you will not go too far wrong having a look at The Good Pub Guide and we recommend that as a good read

Traditional Pub

Here is the tour I went on and am recommending:

Pub Tour of Historic Greenwich

We found this and thanks to them at SightseeingTours.co.uk