There is a sign in the shop saying that photography is not allowed; a sign which I had missed.
Nonetheless, nobody pulled me up on it. Although they did for another person who is trying to take a picture with their phone rather than a DSLR.
Go figure.
Anyway, enjoy this illicit photograph. I should point out that at the very least it is worth paying a visit to the souvenir shop if you're in the neighbourhood. Yes, it is typical tourist trap stuff, but it's at the high-quality end of things. Originally I wasn't going to buy anything, but in the end I caved and bought a Baker Street fridge magnet which is now proudly attached to the refrigerator. I probably paid a little bit more than I should have for it (£5 if I remember correctly) but the purpose of a memento isn't to provide value for money so much as to provide a memory.