Clock-watching staff at a leading auction house sparked a terrorist alert when they turned off the lights and locked up for the night.
For trapped inside Sotheby's in the darkness was America's Ambassador to the UK with his two bodyguards - convinced they were about to come under attack.
The envoy, Robert Tuttle, was viewing an exhibition of Impressionist and modern art - including a work by Picasso that later sold for £7.4million - when the drama unfolded.
Fearing something was wrong when the lights went off, Sotheby's deputy chief...