Muslim communities in the UK have come under intense since 7 July 2005 (7/7), and the emergence of a home-grown threat raised concerns not just about the threat of future attacks, but it also played on deeper anxieties about Britain’s growing diversity and apparent loss of a cohesive identity. Many theories have been offered about the drivers or causes of radicalisation, but they are rarely able to prove more than the exception, never the rule. In fact, it is almost impossible to say with any certainty what the causes are as it is so difficult to know whether a factor is instrumental, or merely present. It is perhaps more helpful to think about ‘radicalising agents’ – factors that are present (though not necessarily causal) and which appear frequently across different cases. This paper sets out the position of Muslims in the UK, the threat to the UK from al-Qaeda-linked and -inspired terrorism through an account of the main terror plots, outlines the main radical groups and movements under the three-pronged categorisation outlined above and closes with an explanation of latest UK government policy responses. It concludes with a note of caution about misinterpreting the nature and intention of these groups and notes the role that many – with some notable exceptions – could play in the effort to tackle radicalisation in the UK.