A lone gunman held up the branch of American Express near Picadilly Circus, in a raid that saw scores of police officers, SWAT teams and dog handlers scramble to the scene, cordoning off swathes of PR1 and trapping staff from both Edelman PR Worldwide and Lighthouse PR in their offices.
A team from Lighthouse - returning from a client meeting as the stand-off began - were forced to retreat to trusty local boozer The Red Lion to continue their high-end discussions on strategic communications.
Things were slightly more frustrating at Edelman, where the seven- hour siege - which ended when cops led away the alleged perpetrator - resulted in staff resorting to supplies of biscuits, bread and booze.
It could have been much worse for the world's largest independent PR firm, as a rumour that the robber was armed with a bomb led to the evacuation of parts of the building, according to European director of human resources Liz Fraser.
'A number of us are next to the wall through to the bank, so the police evacuated us to the other side of the office,' she tells Diary.
But all is well that ends in stoical resignation. 'After an hour and a half we got bored and went back to our desks,' she sighs.