Andrew Parker says the threat from IS “shows no sign of abating” after more than 750 British extremists travelled to Syria.
The PM will not say whether families will be worse off in April because of tax credit cuts – even with changes to soften the blow.
Mr Cameron’s allies claim leaving the EU could still cost the UK hundreds of millions of pounds and may not help cut immigration.
A friendly challenge with former service personnel sees the suit-wearing mayor unceremoniously yanked onto the turf.
In an interview with Sky News, the Chancellor vows to continue with tax credit cuts to deliver a “low welfare, high-wage economy”.