DFC, thanks for your reassurance but with the possibility for an aircraft to route from, say, over the UK midlands direct to Brindisi, ATC co-ordination based on the conventional route structure is not easy - and the difference between great circle and rhumb line may no longer be insignificant.
As for the procedural situation, one of the ways that capacity increases are expected to be achieved is by the use RNAV-defined routes that may not be radar monitored. Other plans are for closely-spaced RNAV-defined routes where it is unlikely that in the worst case scenario a controller, even if he/she happens to be watching the traffic pair closely at the apposite moment, will have time to do anything if an aircraft deviates from the prescribed route (so, one argument goes, why bother with the controller?).