Earl’s Court Square – Fascinating Building, how did they achieve the Glasbox on the front?

Yesterday I noticed this constructing in Grand Design: Home of the Yr: https://youtu.be/nrCWBxyokIA?si=5PwqqJzW754AtqET&t=2893 and I used to be utterly fascinated by the development of the Glasfront with Home windows and Roof assembly on the edge with practically no visible profile.

At the very least for me there’s additionally no perceivable means how rainwater leaves the Glas because it appears to be compeletely flat. Up to now I discovered 5% because the minimal for Conservatory Glasroofs for instance.

Can anybody clarify a bit extra how they achieved it or level me to some ressources?

I anticipate that its prohibitivly costly to assemble however I would love to be taught a bit extra.