  The Square Kilometre Array telescopes have recently started their
construction phase, after years of pre-construction effort. The new SKA
Observatory (SKAO) intergovernmental organisation has been created, and the
start of construction ($\mathrm{T_0}$) has already happened. In this talk, we
summarise the construction progress of our facility, and the role that agile
software development and open-source collaboration, and in particular the
development of our TANGO-based control system, is playing.
