Not all the work involved is visible, and access to the track - with no trains running - is often required. Checking the wiring is exactly where specified; pre-energisation checks that nothing is going to short it all out when turned on. There’s an awful lot of route-miles to check; on some of the busiest railway in Wales. In the 1920s and 30s the railway didn’t have the same duty of care to prevent injuries or worse to its workforce. The human right we now take for granted to do our job without fear of injury or worse was only just starting to be formalised. They were allowed to make major changes to infrastructure between trains; and if a handful of workers were killed or seriously injured in the process, oh well. The railway is a completely different industry to that 80 years ago; with different objectives and different rules to comply with. The southern railway of the 20s and 30s wouldn’t be any quicker if it had to comply with today’s regulations; and the consequent risk to safety would not allow you to remove the regulations that slow the pace of works down.