A man with a car, a knife and murderous intent -- the London attack shows the "new norm" of low-tech terror, experts say.
Analysts who have studied similar attacks say their crude nature makes them almost impossible to prevent and easy to copy, posing a major headache for security services.
The Islamic State group on Thursday claimed the attack on the British parliament that left three dead, saying it was "carried out in response to calls to target coalition countries".
In 2014, IS's then propaganda chief Mohammed al-Adnani urged sympathisers in the West to attack "unbelievers" wherever they were and with whatever came to hand, with police and soldiers a particular target.
In Thursday's attack, a man mowed down pedestrians on Westminster Bridge before jumping out of the vehicle and stabbing to death a policeman before he was shot dead.
- Berlin and Nice -
The attack was reminiscent of three other attacks in the West in the past eight months.
In December, a 24-year-old Tunisian drove a stolen truck into a Christmas market in Berlin, killing 12 people.
Last July, another radicalised Tunisian, who like the London attacker was described by Islamic State as one of its "soldiers", ploughed a truck into crowds watching fireworks in the southern resort of Nice, killing 86.
The United States has also been targeted by low-tech attackers apparently acting alone.
In November, a student used a vehicle and knives to injure 13 on a university campus in Ohio.
Over the past decade, Israel has seen a growing number of vehicle ramming attacks, particularly in Jerusalem, with Palestinians using cars, trucks or even tractors to randomly mow down pedestrians, soldiers or police.
In the latest deadly incident in January, a Palestinian drove a truck at a group of Israeli cadets, killing four and wounding another 15.
Back in Europe, less than a day after the carnage in London, a man was arrested on Thursday after he tried to drive at high speed into a crowd of people in the Belgian port of Antwerp.
Emily Winterbotham, a research fellow at the London-based Royal United Services Institute (RUSI) specialising in extremism and radicalisation, said it was inevitable there would be more such attacks.
"Attacks of this nature, the willingness of someone to use everyday objects, cars, knives, are incredibly difficult to prevent," she told AFP.
They "seem to be the new norm and we can do everything as far as possible to prevent them but they do happen and we need to prepare for that in order to respond in an appropriate manner".
- 'What can you do?' -
And Britain has been here before -- in 2013, two jihadists knocked down solider Lee Rigby outside his barracks in south London and stabbed him to death.
The danger of extremists using cars and crude implements to carry out attacks could be higher in Britain than elsewhere, because guns are harder to obtain than elsewhere in Europe, according to Otso Iho of Jane's Terrorism and Insurgency Centre (JTIC).
"Strict gun-control laws in the UK, and the difficulty of acquiring automatic weapons, even on the black market, decreases the likelihood of mass-casualty shooting attacks," Iho said.
"The risk that vehicular attacks will therefore be used as the most likely tactic of a lone actor intent on conducting mass casualty attacks in the UK is elevated."
Yves Trotignon, a former analyst for France's intelligence services, said Britons could take some comfort from the prompt and competent response of the British security services to Wednesday's attack.
"They responded quickly and they responded well and the (attacker) was quickly killed," Trotignon said.
"The British have been preparing for this for years. If you are prepared for it, the consequences can be minimised.
"But obviously, you are vulnerable to this type of attack. The attacker was armed with a kitchen knife and a car. What can do you against that?"