I was looking at a map of Chesterfield the other day and was quite surprised to find that there is a substantial tunnel beneath the town, which once connected the Chesterfield Central branch to the GCR main line, thereby creating the "Chesterfield Loop" between Staveley, Chesterfield and Heath. I think Chesterfield Central was used by a number of main line or semi-fast passenger workings, but I was wondering if there were any locomotive restrictions on this circuitous loop - in other words, was it used by the largest GCR/LNER locomotives?