If the city is in its own column its pretty easy to do
highlight the entire sheet
then click on data tab and then sort
select the row that city is in to sort on
that will put all of the rows with London next to each other. You can then copy and paste that entire block into its own spreadsheet
There are other ways to do it depending on what end results you wanted but that one is the simplest to do in terms of having any programming skills and what you see is what you get it works very easily and you can see right away what it did and how to use it.