Section 20 was an elite covert British military intelligence and counter-terrorism unit, originally formed within the Secret Intelligence Service (SIS). The unit travelled around the world covertly neutralising terrorist threats against the United Kingdom and their allies. Section 20 could mobilise immediately and have their mobile command station (known as "The Crib") up in a matter of hours.
Focussing on high-risk and top-priority targets, Section 20 is capable of moving from country to country anywhere in the world. Sometimes with the agreement of the countries government, sometimes not.