Let’s sanity-check some magnitudes.
That Property Week article puts Canary Wharf Group as the biggest property owner with 21.5m sq ft.
London has 8.6m residents with 2.5 per average household. Assuming a mean 500 sq ft per household there’s 8.6m / 2.5 * 500 sq ft ~ 1,720m sq ft of just residential property (while the Qatari number includes office space.)
So let’s consider some more: who owns most of the real estate in London?