https://www.quantcast.com/about-us/

....and there's a London address....

let's have a look, then....

https://www.google.co.uk/maps/place/Endeavour+House,+189+Shaftesbury+Ave,+London+WC2H+8JY/@51.5151886,-0.1294512,17z/data=!3m1!4b1!4m5!3m4!1s0x48761b32cc1770b3:0xf35d9d698a69cc9d!8m2!3d51.5151853!4d-0.1272572