Even so, that does seem cheap for a 3-bed flat in Knightsbridge. I'm guessing this is a leasehold property with a relatively short tenure, information that is curiously missing from the sales page.
BTW: I don't think we owned it. We lived in some very nice places, as I was growing up, but my father didn't make that much. I think his company (it used to be "The Company") owned or leased the properties.