This paper analyses a corpus of UK policy documents which sets out national security policy as an exemplar of the contemporary discourse of counter-terrorism in Europe, the USA and worldwide. A corpus of 148 documents (c. 2.8 million words) was assembled to reflect the security discourse produced by the UK government before and after the 7/7 attacks on the London Transport system. To enable a chronological comparison, the two sub-corpora were defined: one relating to a discourse of citizenship and community cohesion (2001–2006); and one relating to the ‘Preventing Violent Extremism’ discourse (2007–2011). Wordsmith Tools (Scott 2008) was used to investigate keywords and patterns of collocation. The results present themes emerging from a comparative analysis of the 100 strongest keywords in each sub-corpus; as well as a qualitative analysis of related patterns of the collocation, focusing in particular on features of connotation and semantic prosody.