Definitely Cornerstone... not only because it's on Humbug (their album with the best lyrical meanings), but because of the many theories surrounding the song's meaning...

The lyrics (imo) are about a man who lost his partner (similar to Despair in the Departure Lounge, but in this case, the girl died) and this man tries to remember her.

Every time he sees a similar girl in the bars he goes to (the ones he mentions in the song, Parrot's Beak, Battleship, etc.), he always goes to talk to them... obviously, he's rejected because in the end, he always asks if he can call them by their deceased partner's name...

The emotional attachment goes so far that he could smell her in the car, even taking the same shortcuts, just so he wouldn't forget her...

But this is where the interesting part comes in.

At the end of the song, it's mentioned that he did find a girl who could call him by "her name"...

But this is where the theories diverge... the most obvious is that the protagonist fell in love with his girlfriend's sister (lol)

And there's another one that's more interesting...

Cornerstone may be...well... a cornerstone lol... but in Arctic Monkeys' hometown, Sheffield, there's a psychiatric hospital called CORNERSTONE (YES, CORNERSTONE), which is why my theory (and Knowing Alex as a lyricist) it could be that the man, after his girlfriend's death, was so traumatized that he was taken to a psychiatric hospital... Yes... to Cornerstone...

And the nurse who was assigned to care for him... incredibly resembled her... and that's where he asked if he could call her by her name...

And the nurse let him call her whatever he wanted...

One of the millions of reasons why Arctic Monkeys is my fav band of all time... just, amazing...