As noted upthread there were various routes taken over the years after sleeper services were concentrated on Euston and the WCML. One issue was accommodating passengers between the WHL and Glasgow. As mentioned when running via Mossend this was achieved by running via Queen Street High Level whether via Springburn or later via Stirling. Then came routing via Central Low Level but without stopping there so a connection was provided at Dalmuir with a similar arrangement after re-routing via Edinburgh and Croy. At some point the Fort William and Inverness services were merged and eventually came the decision to run a single train, nowadays known as the Highland Sleeper, conveying all 3 portions (ie adding Aberdeen) making the Edinburgh route effectively permanent though of course there are still different routes possible between Edinburgh and Glasgow.
However in the late 80s/early 90s Fort William still had a separate train with both day and sleeper coaches and which also ran, at least for a spell, via Birmingham New Street. In April 1989 I did the up service which ran via the Argyle line and then into Central High Level for electric haulage forward (this was a Sunday night so could have been an engineering related diversion). By September 1991 the route was via Edinburgh: I did it in both directions and the down went via Falkirk High with the up via Grahamston.
