Barriers are going up around Europe. Hours after a terrorist in a van mowed down pedestrians on Barcelona’s Las Ramblas last week, Madrid installed massive plant-pots at Puerta del Sol in the Spanish capital. Entrances to the Galleria Vittorio Emanuele, leading to Milan’s cathedral, are blocked by ugly new jerseys, as Italians call them — the modular concrete lane separators first used in the US state.

Nice, victim of the worst vehicle attack to date, has only recently unveiled a white truck-resistant pillar-and-cable fence, cordoning off the Promenade des Anglais, where 86 people died on Bastille Day last year. London, hit by two attacks this year, has reinforced pedestrian walkways on bridges with concrete blocks.

To the acute pain of further loss of innocent lives — tourists, shoppers, revellers — add the sinister, hard-to-define threat to something quintessentially European: the paseo, the passeggiata, the promenade.