A planned rise in the numbers of elite counter-terrorist police marksmen has yet to hit its target as a senior officer admitted challenges in recruitment.
Police chiefs revealed on Thursday there had been a 70% increase in the ranks of the most highly trained armed officers over two years but the pool of counter-terrorist specialist firearms officers (CTSFOs) still needed around 100 recruits.
Plans were put in place to increase the number of all armed officers in the wake of the terrorist attacks in Paris in November 2015, in which 130 people died and hundreds more were injured.
In April the following year the Government pledged £143 million over five years to fund the boost.
The latest figures show that Home Office forces which were given funding have seen an increase of 874 armed officers, up from 640 in April 2017.
When other Home Office forces without funding and non-Home Office forces, such as the nuclear and defence police, are included, the increase rises to 1,351.
The number of Armed Response Vehicles (ARVs), driven by regular armed officers, has also risen by around 27%, in line with plans announced in 2016 to increase the number to 150.
This means that in any 24-hour period there are 55 more ARVs on patrol in England and Wales than there were in April 2016.
Simon Chesterman, the National Police Chiefs' Council lead for armed policing, said the challenges in recruitment included that those selected for the elite role were from a pool of regular armed officers, who then had to be replaced to meet the target.
"It's made the ARV uplift even more challenging because we are recruiting from the ranks of ARVs to become CTSFOs and therefore we are constantly having to backfill," he said.
"Delivering the uplift has been a bit like filling a bath with the plug out."
CTSFOs are trained with special forces to deal with a raft of situations including hostage rescues, and can use boats and aircraft if needed.
Mr Chesterman added that the training and demands of being a CTSFO meant there was a high turnover rate, while some officers wanting to specialise in firearms were put off by fears of the treatment they might face after they pulled the trigger.
He said that while officers welcome "the most intense post-incident scrutiny" if they shoot someone, any investigation must be carried out quickly.
"If they discharge a firearm in public clearly it needs to be investigated and they welcome that scrutiny," he told the Press Association.
"We just have to make sure that scrutiny is swift, because I've known investigations take up to 10 years before an officer was actually taken to court and subsequently found not guilty.
"On average these things are taking years - that's not fair on the officer and especially not fair on the bereaved family."
The total number of marksmen is still lower than it was in March 2012, when there were 6,756 in England and Wales.
This figure steadily decreased until March 2016, when there were 5,639, and then rose to 6,278 the following year.
Originally the increase of 1,500 announced in 2016 was planned to take 18 months, but two years on, as rank-and-file group the Police Federation predicted, the positions have not yet been filled.
Tactics have also changed, with officers allowed to shoot at the driver of a vehicle being used to mow down pedestrians; and in a mass shooting scenario to leave casualties behind to focus on stopping the attacker.
And CTSFOs will be issued additional equipment, including night vision and silencers, to improve their ability to deal with siege and hostage situations.
Mr Chesterman explained that police bosses had done detailed analysis to decide which parts of the country needed more armed protection.
"We can't put an armed police officer on every street corner everywhere across the whole of the United Kingdom, so what we've had to do is analyse the threat, we've had to analyse intelligence, we've had to analyse crowded places, population - there are many layers of the analysis that we've gone in to, to understand where is best to place these officers in terms of where they're most likely to be needed," the deputy chief constable said.
"Of course there are communities within England and Wales where an attack is highly unlikely, where it is very unlikely that something will happen, but ultimately if something does happen we have got to be able to provide an armed response."
He said routine arming of front-line officers in forces with remote rural communities was "not off the table" but said: "I think it does not need to happen at the moment."
After the Westminster Bridge attack last year, terrorist Khalid Masood was shot dead within 80 seconds, while at London Bridge the three assailants were all shot eight minutes after the police were called.