Having been watching the progress of the single line working, it strikes me as to how they’ve made the section from Penrith to Tebay, rather than making use of the emergency ground frames at Clifton & Lowther and the points at Shap Summit. In fact, the trailing crossover at Harrison’s Sidings could be used in lieu of Clifton & Lowther (albeit requiring a reverse).
Carlisle is one of the few boxes left with a relative abundance of trailing and emergency crossovers - I’m surprised they’re not being used to their fullest potential. It could dramatically improve throughput at the moment!