I'm guessing that this will be the first time that a Sleeper train has started or terminated at Glasgow Queen Street High Level for many years, possibly since the Scottish internal (Glasgow/Edinburgh-Inverness) Sleepers were withdrawn in about 1990.
If 1S26 splits at Carlisle on 31st March, I presume this means the Glasgow portion will go via Dumfries and the Edinburgh portion via the Tyne Valley and the ECML?
Also, with all lines out of Euston being closed on Easter Sunday 1st April, I guess this means the Sleepers will be the only trains out of Euston that day, so they will either have to open the station specially just for a few hours that evening, or it will be open all day just to use the ticket office and retail outlets (which won't get many customers during the day if they do open). That is, unless that evening's Sleepers go from King's Cross.
BTW, does anyone know what work will be done at Euston that day? I'm guessing that it's in connection with HS2.