Biometric scans must be boosted at UK borders to stop extremists getting into the country, a counter-terrorism policing chief has warned.
Concerns have been raised about gaps in British border security after a rise in the number of guns on the streets in a string of major cities including London, Manchester, Birmingham, Leeds and Liverpool.
Neil Basu, the new senior national co-ordinator for counter-terrorism policing, said "much more" must be done to protect the border, with an increase in biometric scans, and tamper-proof passports.
He told the Press Association: "Just in the same way you can smuggle illegal firearms into a country, you can smuggle people into a country. And if one of those happens to be a terrorist, that's a big problem.
"Society needs to debate what's required. But in law enforcement, I'd say if you want security, you need to improve your biometrics at the borders. Everybody's identity should be checked as they come through a border in a way that is foolproof. Fingerprints, iris scans, the documents need to be tamper-proof. What we need is a debate about what border security really means."
The Scotland Yard Deputy Assistant Commissioner spoke a year on from the terrorist atrocities in Paris that saw extremists kill 130 people in mass shootings and bomb attacks.
The carnage was a realisation that a marauding firearms attack, previously seen in Mumbai in India in 2008, could happen on Britain's doorstep.
Mr Basu said: "Paris woke us up to the fact this could be in Europe. And in a major capital city not a couple of hundred miles from our shores, from our own capital city. Our heart went out to them, and it was a tremendous 'sit up and think' about how could we respond to something similar. What changed our assumptions were the sheer number of attacks and the breadth and spread of the attacks, and our ability to respond as quickly as possible.
"The terrorist tactics are very different now. They are not interested in negotiation, they are not interested in warnings, they are very interested in the maximum amount of terror, damage and economic and physical and emotional carnage."
In the wake of the attacks in France, police worked to map crowded places and with major sites like stadiums to sharpen security. More officers are sent abroad to gather intelligence, and help protect holiday destinations where it is potentially easier for terrorists to operate.
Plans were also put in place to boost the number of trained firearms officers in the UK by 1,500. Around an additional 100 will be added each month from now until the total is reached in March 2018.
Policing chiefs are looking at potential gaps in armed coverage across the country as they decide where the marksmen will be based, amid concerns that officers in rural areas could face a long wait for back-up.
The armed officers will face "battlefield" conditions as they are trained to leave casualties behind and prioritise shooting terrorist gunmen.
Mr Basu said: "Our firearms officers will go forward, they are trained to stop a terrorist attack. They are not trained to identify it, locate it, contain it, negotiate - they are trained to stop.
"What that means for those officers is they may have to respond, and they may have to do that while people are dying around them, including their own colleagues. So this is a psychological change in policing in this country, to be able to cope with what would be a battlefield or a war scenario."
The highest trained officers are expected to meet similar standards to military special forces. Plans have been made for the military to work under police control in the event of a mass shooting attack.
Currently only around one in 10 members of the public have watched a safety video, called Run, Hide, Tell, which advises the best way to survive such an atrocity.
Mr Basu said: "The vast majority of people who are untrained are going to freeze, are going to try and run, or they're going to try and stay and negotiate.
"What we're saying to them in Run, Hide, Tell is that you're not going to be able to think clearly, so you need to think about three very simple words that are going to give you a chance of surviving the situation."
The film can be viewed on the National Police Chiefs Council website.