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The TALGA 110 requirement performs two functions, both related to LATCC sector workload. As CM indicated, it provides a standard release point for traffic to Cardiff, thus reducing the coordination requirement for individual flights. It also reduces inter-sector coordination at LATCC as the Brecon (133.6) controller, who is working the traffic north of TALGA on A25, has no knowledge of traffic at 120 or above in the BCN area which is the resonsibility of the Bristol (134.75) controller.
Often, of course, these controllers have time to coordinate a non-standard clearance as they currently sit next to each other at LATCC, and indeed sometimes the two sectors are combined. However, at NERC, there is no guarantee that the two controllers will be adjacent, thus making the coordination process more complex.
As regards the direct routing across North Wales, as soon as the military "go to bed" we are granted "off-route" status above FL245. This permits such short-cuts to be made. The hours vary on an ad-hoc basis, but are generally from early evening until 0700 local, and usually all weekend. Feel free to ask if you're flying at those sort of times.
NN