Some kind of ultra-heavy-duty radar dish, for those REALLY energetic, REALLY low frequency radio transmissions. Could also be a radio antenna I guess. Look, I'm not going to tell you what to do.
Part of the "JC Fleet 2" family of models. Get them all here: http://www.peripheralarbor.com/ProjectLondon/

Like this model, but need something a bit different? I take commissions! http://peripheralarbor.com/commission/