The Westminster attack shows the new challenges facing UK counter-terrorism | Emily Winterbotham

The trend towards the easily accessible, low-cost methods seen in London, Nice and Berlin makes preventing attacks ever more difficultOn Wednesday, the wave of terror attacks witnessed in Europe and elsewhere struck at the heart of London. The attacker has now been identified as Khalid Masood, born in Kent – a 52-year-old known to the security services. Isis has also claimed responsibility, although their inability to name the attacker before the police did raises some doubts as to the ver