Don't know much about scotch or whisky in general. Though when I travel internationally, I try to look at the duty free liquor prices at the airport to see whether it is worth picking up a bottle on the way back to Seattle.
World of Whiskies is located in Terminal 5 at Heathrow Airport and offers a selection of whiskies from around the world. The bulk of the offerings are from the UK and Ireland, though I did see some Suntory whisky here too. Though being in the UK, I was in search of a nice bottle of scotch to bring back.
The selection here seems to be similar what I would find at liquor stores in Seattle, though the prices seem better. For instance, you can get a bottle of Lagavulin 16 here for about half the price you would pay at Total Wine & More in Seattle. Not sure about sampling whisky here, though I did try a sample of the airport exclusive Johnnie Walker Island Green scotch that the store seemed to be promoting a lot.
If you do decide to shop here, I would do a price comparison on the bottles you are interested in to see if they are worth the price and trouble of lugging across the pond. Also, I would only recommend picking up a bottle only if your next destination is your final stop. If you have to take a connecting flight, you are not going to be able to take it through security because of the liquid size limits. read more