From GOP USA:

Police chiefs are struggling to recruit enough officers willing to carry a gun to tackle a Paris-style terror attack, because they fear they will be treated as criminal suspects if they use their weapon in the line of duty, the country’s top firearms officer has warned.

After November’s terrorist gun and bomb attacks on Paris, senior security officials believe Britain needs an extra 1,500 armed officers. But because half won’t make it through rigorous training and selection, police chiefs need 3,000 volunteers to come forward.