Terror fight puts unsustainable strain on police: UK top cop

Chief Constable Sara Thornton said resources were being diverted from mainstream policing in England and Wales, leading to backlogs in police control rooms and slower response times.

So far in 2017 there have been five terror attacks in the UK, killing 36 people.

Four people remain in police custody following last week's explosion at a Tube station in which 30 people were injured.

The number of arrests made for terror-related offences in the UK jumped a record 379, up 68 percent in the last 12 months up to June this year, according to figures released by the Home Office.

Thornton told BBC Radio 4's Today programme: "When we respond to the sorts of attacks we saw only a week ago, it's not just our counter-terrorist police units, but the whole system of policing that responds. "The current level of terrorism, added to the strain and stress the force is already under, is causing real problems and is frankly unsustainable."

She said having officer numbers at 1985 levels and crime figures up 10 per cent in the last year created additional pressures.

"After Manchester attack, of the officers and staff that responded, three-quarters were paid for out of mainstream policing." The current funding for forces across England and Wales is "no longer enough" and the counter-terrorism policing budget will be cut by 7 per cent in the next three years, she added. She said a response would "never be as good as preventing" attacks in the first place.

Metropolitan Police Commissioner Cressida Dick said her force would "have to make hard choices in the future".

Earlier this year, Metropolitan Police Assistant Commissioner Mark Rowley said that the counter-terrorism policing network was not able to operate at "full strength".