Terrorist attack Westminster, page-111

Might be that they are a well functioning intelligence service on a much smaller budget than Homeland Security, NZSIS, CSIS, ASIO, ASIS and the DMI. And so they are more effective.

Or Prime Minister May's country might be just more efficient in these things than the other five powers and Eire not to mention old Europe and wherever else in the Non (or should it be Anon)-English Speaking Background (NESB) world where they might or may have Intelligence or intelligence.