Not as a serious other-side but I knew an engineer associated with ARUP and during the time of Canary Wharf being in design, the plenum spaces were re-sized twi

Not as a serious other-side but I knew an engineer associated with ARUP and during the time of Canary Wharf being in design, the plenum spaces were re-sized twice as a function of emerging pre-fibre burdens. I believe now, there is probably the equivalent of 3 or more floors of unused space, consumed by oversize plenum in the light of emerging fibre. I do believe fibre probably is a sensible end road for "small enough" and so pulling more of it, for the same radial bend and cable diameter probably makes sense. Also bear in mind "re clocking" by tuning the lambdas and deploying new lasers is a thing. That 100 pair fibre can be re-clocked across it's lifetime and be the equivalent of 1000 pairs in equivalent bandwidth, by the time you're done.