Agreed, @OrchidInTheSun. There are countless places in Tate Modern where someone could, in practice, throw someone from a height — from the viewing gallery overlooking the Turbine Hall, from the front balcony overlooking the Millennium Bridge at St Paul’s, over the bannister of the staircase in the Blavatnik wing. But you could equally throw them off one of the bridges with equally lethal effect. You can’t net over everywhere.
My blood has repeatedly run cold since I heard this, especially as I was there with my seven year old only a couple of days ago for the Olafur Eliasson exhibition, but you can’t childproof the world against this kind of random attack.