as you can see the transition in the shadow area is render pixalated or flat even though the entire mesh is in smooth shading.
Has anyone come accros this before and might anyone know what causes this.
Exactly. This is known as the terminator artifact. Many unbiased render engines suffer from this and you will find dozens of threads about this in this forum already.
Only way to solve this in Cycles is to use a light source with a “softer” shadow/light transition and/or to massively increase the density of the geometry, e. g. by subdividing it.