The Anti-Terrorist Branch (also called SO13, from its Specialist Operations designation) was a branch of the London Metropolitan Police established to respond to terrorism. Originally dealing with bombings by anarchist groups, it took on the campaign against the IRA in the course of the 1970s, alongside Special Branch and the Security Service (MI5).

In 2005 the Branch had 345 members, and funding for another 500 was being sought. The Metropolitan Police Commissioner, Sir Ian Blair, announced that Specialist Operations units were to be re-aligned. The plans included forming 3 new departments within Specialist Operations to carry out specific functions:

Protection Command (protecting people - splitting the functions of both SO14 & SO16 and merging them with parts of SO17, SO18 and SO12)
Security Command (protecting places - splitting the functions of both SO14 & SO16 and merging them with parts of SO17 and SO18)
Counter Terrorism Command (merging SO12 & SO13 together)
The final head of SO13 prior to the reorganisation was Peter Clarke OBE.

http://en.wikipedia.org/wiki/SO13

Спасибо, но в словарь общей лексики я бы вносить этот отдел не стал. Возможно, составители страноведческого словаря решат включить его в свой словник.