NERC Dweller,
Thanks for your response. Sorry I upset you and on reflection, I could have worded the last paragraph better. What I was trying to say is that the ATC experts (obviously not you, as you admit) could have been led to believe that certain system features were acceptable and hence their modification was deferred until after "O" date. We really need to know what these might have been.
I believe the Claxby radar would always have been the firstchoice radar for the block in question under the West Drayton system. I don't really see your point regarding reducing separation. This procedure increases the ATC team load because of system deficiency. The SI says that the problem will be solved when Mode S is introduced. We don't have any timescale for this in Swanwick (or none I know about). An engineering solution would be ideal but you are the first on this thread to suggest that it is possible. Is it?