Thankyou for beating me to it: this is an example of an unfortunate Amero-centric world view. Go anywhere else in the world (outside the US) and people will immediately understand where London is. Indeed for the vast majority of the world there are no other places of that name.
This may be so, but I’m of the opinion that there are contexts in which it’s helpful to be specific.
A friend of mine from here in England spent some time in Ontario (Canada). On one occasion he was approached by a stranger, who’d been taken by the hat my friend was wearing, and asked him where he’d bought it.
“Oh, I got this in London,” said my friend.
“Excellent! I’m going up there on Saturday! Where…”
“Ah, sorry, I meant London, England.”
From my experience of this message board, I’m fairly confident that, if the OP hadn’t specified which London was the topic, we’d by now have had several posts extolling the virtues of a variety of Londons, one or more posts from GeddyClaypoolBurton explaining which city he was particularly thinking of, followed by a pedantic wrangle over who was being more parochial and/or wilfully obtuse.
Because that’s what we do. 
Home.
When I think of London I think of its many beautiful shades of grey.
I lived in London a long time ago.
Walking through the streets of Soho in the rain.
Or have been watching too many period dramas! 
I live in London and didn’t blink when I saw it described as “London, England”. Thought it was a joking reference to the start of Dangermouse…
Since I lived in Oxford and traveled to London mainly to do research, my memories of London are a little different…
Dirt. London just seemed to have a lot more dirt–in the air, on the streets, on the buildings, on the vehicles, on some of the people even–than Oxford. Strange because Oxford has a reputation for smog, but that’s just what it seemed like.
Activity. It seemed like everybody was racing in a different direction to everyone else.
Crowds. At times overwhelming. My ex once had a panic attack on an overcrowded London street and I had to carry her (literally) into an office building to get away from everyone.
Multiculturalism. You could meet someone from anywhere there. That was pretty cool.
Orderliness. Despite all of the above, there seemed to be a pattern to everything. Nobody seemed to be flustered by anything and everybody carried on. Case in point: I was at the Tottenham Court Road platform, in one of the deepest parts of the Tube system, when there was an “incident” and the whole station had to be cleared. A Tube worker opened the door to a “secret” staircase and told everybody to start climbing. In other cities you’d hear complaining or panic…not here. Everyone just started walking up the stairs, hundreds of stairs. Not only were people not upset about it, they were positively jolly! There was an elderly woman who I helped up some of the stairs, and after we got to the top and she thanked me she said, “I’ve been taking the Tube for years and I’m glad I finally got to see those stairs!” That’s the kind of attitude I always associated with London.
Big Ben, the Tower, the Tower Bridge, Madame Tussaud’s, Carnaby Street, Denmark Street, My Fair Lady, Westminster Abbey, the Changing of the Guard, the Underground, London Calling, Heathrow, Guy Fawkes, Waterloo Sunset, Trafalgar Square.
double decker buses and black bear skin hats
Westminster Abbey. The tower of Big Ben. The rosy-red cheeks of the little children.
“If you like the food, you’ll love the weather.”
Spent 10 days in London every year for about 7 or 8 years on business.
- Nice people.
- Great pubs with flat beer filled to brim.
- Odd pub hours (in those days).
- Great night clubs.
- Everything a bit pricey (and I was living in Berlin, not exactly a cheap city either).
- Great shopping for cool, interesting clothing and music and books.
- Cheap theater compared to other large cities; see a stage show for price of movie in NYC.
- Screaming every time a taxi turned the corner (it doesn’t seem natural to drive on left.)
- Really good Indian food - but truly horrible, greasy, fish and chips.
- Bad coffee.
- Lukewarm, out-of-the can, baked beans for breakfast?!?! Yuk!
- Vegemite (or that other obnoxious variety starting with “m” that I can’t remember) that is an acquired taste similar to eating turpentine in a gel form.
- Fun things to do, even though they are “touristy”, but great museums and art and architecture and history abound.
- Amazing public transport - easy to get around everywhere!
Despite the many minor quibbles, I really like London - loved going there every year and looked forward to it - but wouldn’t want to live there. I would love going back for an annual visit every year if I could.
How do they miss the instruction telling them which way to look?
I spent a summer there over 30 years ago. Fond memories:
-Poon’s Chinese restaurant with wind-dried duck
-the constant tang of diesel fuel from black cabs and buses
-practising with the Hampstead Heathens women’s soccer side (on beautiful Hampstead Heath, of course)
-drinking in pubs with male and female Heathens
-going to a couple of Tottenham Hotspur games and being considered a toff for buying a seat instead of standing in the terraces
-seeing wonderful live theater at least 2 nights a week (a lot of John Wood, Tom Stoppard, and RSC)
-feeling safe riding 7 miles home on my bicycle at 11 pm from said theaters
-the wonderful aroma of night-blooming jasmine outside of the windows of the Haringey group house we shared
But this one is etched in memory.
Early 90s.
Bachelor accommodation provided by our company, had many rooms on sharing basis. I had a spacious room and my loo was frequented by our accounts guy, as he found it very comfortable to sit than his own cramped loo.
“London” used to be a slang for taking a dump.
I was an avid listener of BBC word service radio. One day accounts guy was just stepping into the loo with one leg already inside, when Owen Bennett-Jones announced " This is London" loudly in my radio. Accounts guy just froze there .
That was one of the few occasions when I laughed uncontrollably as a grown-up.
Yep! My gf and a coworker went to London last year, and brought me home a “Mind The Gap” hat. Amazingly, many people have no clue what the phrase means.
Their tour of London involved Pubs and Cemeteries. They would hit some bars, catch a buzz, then check out a cemetery.
Olympics!
Your gf should have got one of these for herself!
Your link doesn’t work.
Hah! Will do. Thanks.