on an uncertain emission line at 4854Å assumed to be  $\lambda 1640$ and the possible detection of an associated Ly$\alpha$ break. This redshift was assigned a quality “$\gamma$”, indicating an “uncertain” redshift. Here we report the first robust spectroscopic redshift for C, confirming it to instead be at $z=1.58$, and examine the surrounding cluster environment. Section \[sec:method\] outlines our data and methods used. In Section \[sec:spectrum\] we present a new, deep, optical spectrum of C which confirms its redshift as being $z=1.58$. Section \[sec:results\] then investigates the properties of the galaxies surrounding C, and Section \[sec:conclusion\] presents our conclusions.

In the following, all magnitudes and colours are in the AB photometric system and we assume a $\Lambda$CDM cosmology with $H_0=70$kms$^{-1}$Mpc$^{-1}$, $\Omega_m = 0.3$, and $\Omega_{\Lambda} =0.7$.

Data and Method {#sec:method}
===============

Imaging
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The field surrounding C was imaged with *Spitzer*’s Infrared Array Camera [IRAC; @Fazio2004] at 3.6and 4.5by the CARLA survey [@Wylezalek2013], reaching a $3\sigma$ depth of $23.8$mag and $24.4$mag at 3.6and 4.5$\mu$m, respectively. This field was identified as a protocluster candidate with a $4.5\sigma$ overdensity by @Wylezalek2013 and was followed up in $i'$ and $J$ using the William Herschel Telescope in La Palma. The $i'$ band image was 