Having put more thought into this, I worry that it will cause more pilots to route round Class D, rather than bother to "advance book" a transit, especially when people have been refused a crossing request, which will almost undoubtedly happen (human nature being what it us). There are a number of choke points in the London area and this will possibly make them even busier. Farnborough LARS often struggle to cope as it is due to controller workload, especially at weekends. Flight safety compromised in the name of progress?