We visited with friends for cocktails after visiting last year on my hen party. The service was great and the bar staff were really accommodating in making different variations of the cocktails and suggesting drinks.
It was a shame the usual entrance was closed due to building work, the arrivals process is fun especially if coming for the first time. The menus continue the theme with the cocktails hidden within old books.
I'd also recommend the cocktail classes for groups, really fun.