  In this paper, we investigate sizeable interference effects between a heavy
charged Higgs boson signal produced via $gg\to t\bar b H^-$ (+ c.c.) followed
by the decay $H^-\to b\bar t$ (+ c.c.) and the irreducible background given by
$gg\to t\bar t b \bar b$ topologies at the Large Hadron Collider (LHC). We show
how such effects could spoil current $H^\pm$ searches where signal and
background are normally treated separately. The reason for this is that a heavy
charged Higgs boson can have a large total width, in turn enabling such
interferences, altogether leading to very significant alterations, both at the
inclusive and exclusive level, of the yield induced by the signal alone. This
therefore implies that currently established LHC searches for such wide charged
Higgs bosons require modifications. We show such effects quantitatively using
two different benchmark configurations of the minimal realisation of
Supersymmetry, wherein such $H^\pm$ states naturally exist.
