  We present a list of 15 clusters of galaxies, serendipitously detected by the
XMM Cluster Survey (XCS), that have a high probability of detection by the
Planck satellite. Three of them already appear in the Planck Early
Sunyaev-Zel'dovich (ESZ) catalogue. The estimation of the Planck detection
probability assumes the flat Lambda cold dark matter (LambdaCDM) cosmology most
compatible with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7) data. It
takes into account the XCS selection function and Planck sensitivity, as well
as the covariance of the cluster X-ray luminosity, temperature, and integrated
comptonization parameter, as a function of cluster mass and redshift,
determined by the Millennium Gas Simulations. We also characterize the
properties of the galaxy clusters in the final data release of the XCS that we
expect Planck will have detected by the end of its extended mission. Finally,
we briefly discuss possible joint applications of the XCS and Planck data.
