Context :

Aims : 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 \geq 0.8 .
As part of this project , we analyse the deep XMM-Newton exposure covering one of the CFHTLS deep fields to quantify the cluster content .
We validate the optical follow-up strategy as well as the X-ray selection function .

Methods : We searched for extended X-ray sources in archival XMM-Newton EPIC observations .
Multi-band optical imaging was performed to select high redshift cluster candidates among the extended X-ray sources .
Here we present a catalogue of the extended sources in one the deepest \sim 250 ksec XMM-Newton fields targetting LBQS 2212-1759 covering \sim 0.2 \Box ^ { \circ } .
The cluster identification is based on deep imaging with the ESO VLT and from the CFHT legacy survey , among others .
The confirmation of cluster candidates is done by VLT/FORS2 multi-object spectroscopy .
Photometric redshifts from the CFHTLS D4 were utilised to confirm the effectiveness of the X-ray cluster selection method .
The survey sensitivity was computed with extensive Monte-Carlo simulations .

Results : At a flux limit of S _ { 0.5 - 2.0 \text { keV } } \sim 2.5 \cdot 10 ^ { -15 } \text { erg s } ^ { -1 } we achieve a completeness level higher than 50 % in an area of \sim 0.13 \Box ^ { \circ } .
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 \geq 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 .

Conclusions : The quest for distant clusters in archival XMM-Newton data has led to detection of six clusters in a single field , making XMM-Newton an outstanding tool for cluster surveys .
Three of these clusters are at z \geq 1 , which emphasises the valuable contribution of small , yet deep surveys to cosmology .
Beta models are appropriate descriptions of the cluster surface brightness when performing cluster detection simulations to compute the X-ray selection function .
The constructed \log N - \log S tends to favour a scenario where no evolution in the cluster X-ray luminosity function ( XLF ) takes place .