First choose the number of cities by typing ‘100’, ‘250’, '500', '1k' or 'all' – then try to achieve the highest population among the largest English cities (min 500 population) you chose. Quiz is not timed.
hugequiz Premium users have the option to choose any number of cities to play the quiz with (stats are processed but score isn't saved). Simply enter #(number of cities)# to play the quiz with any number of cities from 25 to the maximum. For example, to play the 300 largest cities, type #300# to begin the quiz and you will play it with the 300 largest cities. Entering #all# will play it with all cities - all cities will also be chosen for any number chosen above the total.
Quiz Takers 
I think that Saint Petersburg shouldn’t be on here (since it’s 15 letters). And in the “50 hardest” West Bromwich is listed twice
for ‘Saint’ i went with ‘St’ for countries where that is the typical spelling (via the country’s census/Wikipedia/other references to the city) – so for US/Russia and a few others it is ‘St’ whereas French/etc it is ‘Saint’ and other countries may be something like ‘Sankt’.
okay, though I’m pretty sure St. is not a typical spelling in Russia (since Russian doesn’t even have a St. abbreviation)
How long are you going to continue with this series?
If the US series is anything to go by, 14 letters… then a Long Names one for everything beyond that.
yeah long names coming soon for the balance, maybe one more 13-letter one.