Of the 906,464 tests taken between 2005 and 2009, 263,641 were failed (a pass rate of 70.9%). The results of candidates from countries with a strong tradition of immigration to the UK were variable. The pass rates for people from Australia, Canada, New Zealand, and the United States were all above 95%. In contrast, the pass rates for people from Iraq, Bangladesh, Afghanistan and Turkey were below 50%.
With the introduction of testing on the new study material from March 2013 pass rates fell to an average of 70%.
Honestly, this test doesn't seem that difficult considering Meghan had a degree in Public Relations, lived in a Commommonwealth Country herself and was paid to represent Britain as a public figure. She doesn't come out that bright, Harry neither but I'm not surprised.
I try it myself and despite one or two questions the rest is basic knowledge on UK.