Is it common for place names to lose the possessive?
I've always thought it should be 'King's Cross, London' as in a possessive sense. However the wiki page for King's Cross uses 'Kings Cross' in the title and 'King's Cross' throughout the article, and this newspaper article uses 'Kings Cross' throughout. And Google result for 'The King's Singers' returns a page title that reads:
The Official Kings Singers Website :About Us - The King's Singers
I've also seen other names like 'St Albans' or 'Harrods'. I thought these names are also possessive, as in 'Saint Alban's (city)' or '(Mr.) Harrod's (department store)', but the apostrophe seems routinely dropped. I thought maybe there is a rule that says 'drop the apostrophe if it's a proper name for some geographic location or shop name, etc', but 'Sainsbury's' seems to keep the apostrophe more often than not.
So I'm quite confused: am I expected to omit the apostrophe when spelling these names, or what? If yes, what's the rule to follow?