Back in the 1970s (and probably before and after) the Scottish internal sleeper service from Glasgow and from Edinburgh to Inverness had just one composite sleeping car from either Lowland point, combined at Perth. The Scottish Region in fact only had five sleeping cars allocated, and this required four every night, with one spare at Inverness. If they were short they could borrow from the ECML large fleet, but this was regarded as dishonourable and every effort was made, including bringing the spare Inverness car Down South on an afternoon service if one had been failed at the other end, to keep to their own allocation. The train was bulked out by a couple of seated coaches and a considerable number of vans for mail/news/parcels. I wonder if anyone ever got on a berth at Haymarket and off at Waverley.
It was commonly used by Scottish Civil Servants from Glasgow/Edinburgh going to morning meetings in Inverness. A woman colleague there said she would be booked in second class, twin-berth, but as individual women passengers were very rare she always got it to herself in first class style.