Come and see 2,057 pink smiley-faced clouds float over Bankside as British artist Stuart Semple experiments with a never-before-used technology.
The Happy Cloud installation is intended to be a message of hope and positivism in reaction to the doom and gloom of current events.
Weather permitting, one happy cloud (helium, soap and vegetable dye) will be released every seven seconds.
Each cloud should last for 30 minutes.
The best viewing location will be the Millennium Bridge.
Related website: www.stuartsemple.com