Work this one out, if you please.

It is now accepted among the police and counter-terrorist organisations, and across Whitehall, that the threat from jihadis returning from Syria and Iraq is growing.

There are believed to be hundreds of terrorists who will, at some point, return to the UK. The Prime Minister has warned that Isis is likely to be plotting to attack British targets. No wonder the CST is concerned. As it puts it: "We have to work on the suspicion that some may target Jews." Given that the most basic purpose of government is defence - the protection of British citizens from attack - you might think that the sensible response to this heightened and growing threat would be focus more resources on counter-terrorism strategy and intelligence. Instead, the Foreign and Commonwealth Office has responded by halving its counterterrorism budget from £30 million annually to £15 million, removing 35 of the counterterrorism unit's 85 staff. Yes, times are tough and budgets are under strain.

But budget-setting is about priorities. And nothing is more important than protecting British citizens from attack. This is one cut that must be reversed before it is too late.