Hmmm I'm going to say Cleopolis.

I'll guess Paris, though I'd be stunned if there were no English-language histories of that city prior to 1955.

I'd also be stunned for an Englishman to refer to France as "Britain's dearest ally" :)

I'm going the snarky route and say: The US.

Yes, for had they meant Ottawa, they would have phrased it differently.

...oh, surely not Edinburgh.

Moscow?

I think the funniest part is the number of cities it couldn't possibly be.

I gave the copyright date mostly to rule out some of the options; timprov guessed Kyoto until I said the year.

Knowing you, and guessing that it's not going to be the obvious, I'm going with somewhere Nordic. Sweden? Norway? Denmark?

Whoops. Cities. Stockholm, Oslo, Copenhagen?

This is tough, because you'd think that a British writer would also consider historical conflicts before saying "dearest" - which makes me wonder who can possibly be left.

Bern.

But I really want to say Madrid. Except the writer would have to have been in an opium den, with a hookah in hand, to refer to Madrid in that manner.

Lisbon - though oldest, rather than dearest, I would have said.

Ah, that was my thought, too. Do we have any dear allies? I'd have thought we were too superior for that!

In 1955? Riyadh.

Ooh.

I also would guess Lisbon, and then just to play the odds, Helsinki.

That was my guess because it was so interestingly not right.

Well there is the possibility the author meant 'not the cheapest' as in costliest :)

(I just can't quite go with Washington DC not having an English language history - unless, of course, they meant in English not Amglish :D )

Cardiff? Delhi?

I was going to say Delhi! Closest ally = Imperial underlings.

Lisbon?

Cape Town?

Barsoom?

Wonderful idea!