Yesterday I created a portal, teleported into the Nether for the first time since the update, tried to leave the Nether and was unable to teleport - stuck in the purple teleporting phase. On reloading, Minecraft took me back in time to when I hadn't started building the portal. 

Today I rebuilt the portal, teleported to the Nether, walked forwards into the Nether and noticed there is no portal behind me. I am now stuck in The Nether.

What to do...? 

(Windows 10, Java build 1.8.0_251-b08)