Racial profiling to stop Islamist terrorists in London is a Bloody Stupid Idea. Not because it’s morally wrong – if we were being targeted by, say, Black Panthers, then there would be a serious and unappetizing choice facing society. However, this isn’t the case.
Let’s put the actual Islam-vs-terrorism debate to one side for the sake of argument, and assume that the point of this racial profiling would merely be to discover Muslims (who are, presumably, more likely to be Islamists than are non-Muslims).
Muslims of Pakistani origin look similar to Indians. Muslims of Arab origin look similar to Greeks (and Brazilians). Muslims of Indonesian or Malaysian origin look Oriental. Muslims of African origin look African. Muslims of European origin look European.
We can probably assume that Japanese people and Inuit are unlikely to move to the UK and convert to Islam. But beyond that, any racial profiling you carry out will still either leave 95% of the population within its sights, or will rule out people who are just as likely to be Muslims as the racial groups you’re including.