They are aiming to show "we are here and are using same road".
Last two weeks, I know 2 cycler died by car clash. One is in front of our office, the cycler was fallen over by concrete lorry.
I went with them from Clerkenwell through Bank and London Bridge until Elephant and Castl, where had an accident two weeks ago. It is also the cyclist was fallen over by the lorry in round about.
We don't have any cycle lane, someone said that cycling in London is like committing suicide.