Old Street roundabout designs

That strikes me as a very bad idea though.

Advertising by necessity needs to grab attention, do we want one of the most dangerous junctions to have an attention grabbing centre?

To navigate a roundabout you have to look to the inside, I'm not sure that it would be advertising that funds the building, it is the externalised cost of road incidents that would fund the roundabout.

Literally, and trying to avoid being hyperbolic, I think that distracting advertising in the centre of roundabouts brings in revenue for the landlords with a real cost measured in increased road incidents.

I agree. I think whether it's advertising or not, it would be very distracting. I also forgot to add something in the previous post; work by Intelligent Space and others has consistently found that one of the main barriers to pedestrian movement is if views are blocked, and this scheme would introduce a major blockage of views.