Terrace and lawn

I now need to bring the lawn up to the terrace.  Initially the plan was to turn the existing turf over and back fill from the various soil quarries around the garden. But. The soil under the tree is terrible. It is mostly flint and so dry that I'm amazed any grass grows.

So, the new plan is dig out the whole area, sieve out the flint and put the soil back with some of the huge pile of mushroom compost covering the drive.  Another stupid and big job, but my muscles are getting used to it.