I'm a gin girl, there is no doubt. My go to drink is a gin and tonic or a gin fizz. I kept a liter of gin in my dorm room at university; I could go on and on. So, as soon as I saw my London Pass had an option for me to go on the Beefeater Gin Tour for free, I knew I had to go.
The gin tour takes place at the Beefeater Gin distillery at 20 Montford Place, SE11 5DE. To get there I took the Jubilee line to Westminster, took exit 5, turned out the exit to the right and took the 159 bus from stop G at Westminster to the stop Kennington Park Post Office. Then, I crossed the street (backtracking the way the bus went) until I reached a fork in the road and took the smaller left side that took me to a residential street. Once I turned the corner at the end, I could see the beefeater gin sign. It is a bit hard to get to, but since it is the actual distillery, it makes sense it wouldn't be in the center of London.
The tickets usually cost £12 and includes a free gin and tonic (which will set you back at last £5 in London). There is an option to buy tickets online (but you can't use your London pass, at least no so far as I can tell) but I just showed up and went on a tour with only four other people (the max is 15). What I would do is check online the day you want to go and see how many tickets are available. If there are a lot for two tours in a row (they go every 30 minutes) then I would just show up. For the tour, there is also an option to pay extra for an iPad to help guide you but you really don't need it.
The tour set up is as follows: 30 minutes self guided tour through their museum and then 30-40 minutes of a guided tour and then your gin and tonic.
The guided tour included a very nice and entertaining tour guide who discussed the botanicals of gin while giving them to us to smell. Then she talked about the distillation process. You can look up through the glass ceiling to see the actual stills that are being used! Then, she makes everyone a gin and tonic. Afterwards, she encouraged us to go downstairs and ask for “the secret stash” I don't know if this is only available to small groups or what, but they gave an extra small sample of beefeater gin 24 and beefeater London garden (a gin only available at their distillery!)