I was looking at a YouTube video on the Portsmouth dockyard railway. It talks about the Royal Train leaving South Railway Jetty and going direct to Windsor. Assuming this is before WWII^▸ (World War 2 - 1939 to 1945), what is the "direct route" to Windsor from Portsmouth, or Gosport (another Royal multimodal transport hub!).

I found a lot of examples of the wording "direct to Windsor" from Portsmouth in the press, mostly for a few years around 1900. Only rarely it was said explicitly that this was by train (which might only mean that it was obvious) and just once have I found the Great Western station was specified as the place of arrival. A few of the reports refer to Windsor Castle as the destination, though it's hard to say if that implies no reception at the station or even travel by road.

The same wording is used, though less often, much earlier - even before railways - and later, and for royal travel from other places than Portsmouth. It also gets used for military formations, which would at the earlier dates be marching. So I think that the phrase really just means, for royal travel, with no engagements anywhere on the way.

The section of the video shows the royal train leaving South Railway Jetty. Thanks for reminding about the "the now-removed south to west curve at Staines". Presumably it would also have been possible via the now-removed west to south curve at Slough.

Presumably either could have been used by royal trains leaving Gosport, which Queen Victoria used when they were at Osborne. The route would have had to be via Winchester.

The link from Gosport station to the "royal pier" is not shown on Rail Map online but is shown on the 1919 OS^▸ (Ordnance Survey) 1" map on SABRE. Haven't checked NLS^▸ (usually Nailsea & Backwell station, but may refer to National Library of Scotland in an historic map context).