There was no formal indication from the police about the identity of the people who left a silver- green Mercedes outside the club or their intention. But British news organizations referred to the alert as a botched car bomb attack, and it added to a catalogue of summertime security alerts ascribed to jihadists since the July 2005 London bombings and a major airline scare last August.

“We heard an announcement on the tube,” said Sheila Porter, 73, a retired psychologist visiting London from Ireland, referring to the London subway by its nickname. “I tried not to think about what it would be but it did seem to imply that the incident was in the street and not on the tube so that kept us all calm. To be honest, it didn’t worry me because they didn’t tell us what it was and they distinctly said it is not the station [but] it was in the street. We didn’t know about this when we started out but you don’t have any choice but to keep going.”

The alert closed off streets around the Haymarket thoroughfare and brought some people out of nearby offices to find out what was going on.

“It’s only when I got to work that I realized what was happening,” said Renee Anderson, 32, a New Zealander from her country’s nearby diplomatic representation.

“I feel surprisingly all right about it,” she said. “We all kind of thought, well you could be hit by a bus anyway and the English mentality must be such that they have coped with this for such a long time with all the bombings so they just get on with it. You can see that.”