  The XMM-Newton Distant Cluster Project (XDCP) aims at the identification of a
well defined sample of X-ray selected clusters of galaxies at redshifts z>0.8.
We present a catalogue of the extended sources in one the deepest ~250 ksec
XMM-Newton fields targeting LBQS 2215-175 covering the CFHTLS deep field four.
The cluster identification is based, among others, on deep imaging with the ESO
VLT and from the CFHT legacy survey. The confirmation of cluster candidates is
done by VLT/FORS2 multi-object spectroscopy. Photometric redshifts from the
CFHTLS D4 are utilized to confirm the effectiveness of the X-ray cluster
selection method. The survey sensitivity is computed with extensive
simulations. At a flux limit of S(0.5-2.0 keV) ~ 2.5e-15 erg/s we achieve a
completeness level higher than 50% in an area of ~0.13 square degrees. We
detect six galaxy clusters above this limit with optical counterparts, of which
5 are new spectroscopic discoveries. Two newly discovered X-ray luminous galaxy
clusters are at z>1.0, another two at z=0.41 and one at z=0.34. For the most
distant X-ray selected cluster in this field at z=1.45 we find additional
(active) member galaxies from both X-ray and spectroscopic data. Additionally,
we find evidence of large scale structures at moderate redshifts of z=0.41 and
z=0.34. The quest for distant clusters in archival XMM-Newton data has led to
the detection of six clusters in a single field, making XMM-Newton an
outstanding tool for cluster surveys. Three of these clusters are at z>1, which
emphasises the valuable contribution of small, yet deep surveys to cosmology.
Beta-models are appropriate descriptions for the cluster surface brightness to
perform cluster detection simulations in order to compute the X-ray selection
function. The constructed logN-logS tends to favour a scenario where no
evolution in the cluster X-ray luminosity function (XLF) takes place.
