I had planning permission granted for an extension just under three years ago. It expires in June 2010. My contractor will not be able to commence main works prior to this date, but is there anything I can do to demonstrate that work has commenced prior to expiry of the permission so I dont have to re-apply? If so, what is the process? I have heard stories of "lifting a paving slab" consitututing start of works. Do I need to tell the planning authority. How do I prove I've started? Thanks in advance for any advice.