Gin Tasting

There are a number of craft distilleries, as well as some larger ones, in London. I went to the Sipsmith distillery in Chiswick several years ago, at that time they were not offering tours or tastings, but are now, worth looking into... https://sipsmith.com/us/

While in the area, you could stop in at the Fullers brewery for a tour, and the walk along the Thames from there, down to Hammersmith bridge is pleasant, with a couple riverside pubs along the way.

I also looked into the City of London Distillery and Bar, they do tastings, even "custom" distillation.

Probably loads of other options with a search.