We present predictions for deep JWST surveys from the latest version of the galaxy formation model GALFORM. The model provides a physical calculation for 'ab initio' galaxy formation and can reproduce an unprecedented set of observational results ranging from present day (z=0) NIR and optical luminosity functions to 850um number counts. Here, the UV to mm SEDs for the simulated galaxies are calculated through coupling GALFORM with the radiative transfer code GRASIL. We present model predictions for number counts, redshifts distributions, luminosity functions and sizes for the galaxy populations observable by NIRCam and MIRI on JWST. Our 'ab initio' model also allows us to present predictions for the physical properties of these galaxies (stellar and SMBH masses, gas fractions etc.) and to probe the importance of various physical processes, e.g. supernovae feedback, on the formation of the high redshift (z\gt10) galaxy population observable by JWST, providing an essential tool for interpreting future observational results.