A z + H colour composite image (4.5′ on the side) of the environment of XMMU J0338.7+0030 with an overlaid contour map of the X-ray emission detected by XMM-Newton (in yellow). These log-spaced X-ray contours correspond to significance levels of 2 − 16σ; they were derived from the adaptively smoothed, combined images of the cluster environment. Red contours highlight the over-density of galaxies with very red z − H colours (3.0 ≤ z − H ≤ 4.8   Vega   mag), as obtained from the OMEGA2000 imaging (see Sect. 2.2.2). White dashed and solid lines encircle regions within 30′′ and 60′′ from the X-ray centroid of the cluster (RA(J2000.0): 03^h38^m44.2^s, Dec(J2000.0):  + 00^d30^m01.8^s), respectively; they guide the eye. The red contour closest to the X-ray position of the cluster corresponds to a significance of 4.6σ above the mean background.