This is a problem for Theresa May simply because she doesn't want to be accused of being weak on immigration.
The letter is somewhat odd in that it claims there is no evidence that the seperate visa issue puts off Chinese tourists and then immediately states that [only] 1 in 4 that apply for a European visa also apply for a British one.
As you point out Chinese Nationals are not high on the national security Agenda these days so it would be very interesting to know exactly how many people from China with a European Visa have subsequently been refused a UK visa due to "national security" concerns.
I'm guessing a number less than 1
Of course Theresa May is a noted Euro Skeptic and it could just be that she is blocking this for internal political reasons



