  The high resolution spectrograph ESPRESSO on the VLT allows measurements of
fundamental constants at unprecedented precision and hence enables tests for
spacetime variations predicted by some theories. In a series of recent papers,
we developed optimal analysis procedures that both exposes and eliminates the
subjectivity and bias in previous quasar absorption system measurements. In
this paper we analyse the ESPRESSO spectrum of the absorption system at
z_{abs}=1.15 towards the quasar HE0515-4414. Our goal here is not to provide a
new unbiased measurement of fine structure constant, alpha, in this system
(that will be done separately). Rather, it is to carefully examine the impact
of blinding procedures applied in the recent analysis of the same data by
Murphy (2022) and prior to that, in several other analyses. To do this we use
supercomputer Monte Carlo AI calculations to generate a large number of
independently constructed models of the absorption complex. Each model is
obtained using AI-VPFIT, with alpha fixed until a "final" model is obtained, at
which point alpha is then released as a free parameter for one final
optimisation. The results show that the "measured" value of alpha is
systematically biased towards the initially-fixed value i.e. this process
produces meaningless measurements. The implication is straightforward: to avoid
bias, all future measurements must include alpha as a free parameter from the
beginning of the modelling process.
