John Lewis, my nearest one is a mere 10 minute walk away, closed of course at the moment. I'd hate to lose them off the high street.
Yes I remember diving into Simpsons of Piccadilly Dinah many moons ago when I worked up in town, then of course there is Harrods, but I never really liked it that much, well not enough to buy anything, although one of my sons forced me to buy a Star Wars toy there that was 3 times the price of what it would cost locally, but it was a quid pro quo pact he'd set up on the basis that he wouldn't moan whilst we went to an exhibition at The Royal Academy mercenary little git Although I did like to visit the pet department in my late teens, where you could buy a lion if you so wished, as one did back in the day Fortnums lovely to wander around and frightfully naice for a cuppa and a slice of arm and a leg cake!
Not a department store, but Daunt Books in London, if I could be locked in for the night anywhere it would be there.