Britain's most senior police chief is expected to call for "less suspicion and more trust" when officers use firearms.
In his final speech before retiring as Commissioner of the Metropolitan Police, Sir Bernard Hogan-Howe is due to call for greater public support for gun-carrying policemen and women who confront terrorists and armed criminals.
Speaking at the Royal United Services Institute after more than five and a half years in charge of Britain's largest police force, he is expected to say: "When people look at what we do, there should be less suspicion and more trust."
Sir Bernard is also expected to reveal Scotland Yard deployed to incidents involving firearms more than 3,300 times in 2016, without firing a single shot at a suspect.
He will reiterate his concern over armed offenders after a year in which almost 700 firearms were recovered by officers in London and 12 people were shot dead by criminals.
Following the Paris terror attack in November 2015, last year Sir Bernard ordered an increase of 600 highly trained specialist marksmen.
His speech is expected to highlight how plans to increase the number of armed officers is on track, with more than 400 extra being trained or selected to date.
He will also stress that officers who volunteer for a specialist firearms role face a demanding training course, which a significant number do not pass, and that as existing officers retire from the role, others must take their place, meaning the force is always seeking more volunteers.
"This a dangerous place to be - in two ways. We simply don't have enough people now wanting to do these jobs. The failure rate in training is high," Sir Bernard will add.
"Secondly, we can't afford to have officers think twice because they fear the consequences of shooting someone. That's how they get shot or the public gets hurt or a criminal gets away with a gun."
His remarks come after a Scotland Yard survey published on Monday showed that of the 11,000 staff quizzed, 6% believe there is an "adequate" quantity of gun-carrying officers in the capital.
Findings from the Metropolitan Police Federation's questionnaire revealed that 43.6% of respondents said there should be more firearms specialists in the force, but not all officers should be routinely armed.
One in four (26%) said all officers should be routinely armed, while 12% said they would not carry a firearm on duty under any circumstances.
The poll, carried out last month, also indicated strong support for increasing the number who carry Tasers.
Three-quarters said all Met officers should be issued with the stun guns while on duty, while just under a quarter (24%) were opposed.