The flavour puzzle is one of the greatest mysteries in particle physics. A
`flavour deconstruction' of the electroweak gauge symmetry, by promoting at
least part of it to the product of a third family factor (under which the Higgs
is charged) times a light family factor, allows one to address the flavour
puzzle at a low scale due to accidentally realised U(2)5 flavour symmetries.
The unavoidable consequence is new heavy gauge bosons with direct couplings to
the Higgs, threatening the stability of the electroweak scale. In this work, we
propose a UV complete model of flavour based on deconstructing only
hypercharge. We find that the model satisfies finite naturalness criteria,
benefiting from the smallness of the hypercharge gauge coupling in controlling
radiative Higgs mass corrections and passing phenomenological bounds. Our setup
allows one to begin explaining flavour at the TeV scale, while dynamics solving
the large hierarchy problem can lie at a higher scale up to around 10 TeV -
without worsening the unavoidable little hierarchy problem. The low-energy
phenomenology of the model is dominated by a single Z′ gauge boson with
chiral and flavour non-universal couplings, with mass as light as a few TeV
thanks to the U(2)5 symmetry. The natural parameter space of the model will
be probed by the HL-LHC and unavoidably leads to large positive shifts in the
W-boson mass, as well as an enhancement in Br(Bs,d​→μ+μ−). Finally, we show that a future electroweak precision machine such as
FCC-ee easily has the reach to fully exclude the model.Comment: 28 pages, 3 figures, 1 appendix. Version accepted for publication in
JHE