Tell me what to bake...

[DerelictWreck]

For my sister's birthday tomorrow? It needs to travel well via train. I do have a carry cake box but I'm still worried about anything fragile or with whipped cream/ butter icing etc!

Could you make a cake and icing, keep separate and then quickly ice before serving?
Or take cake/ jam/cream, and whip up and smooth on the cream just before serving?

You could do a loaf cake such as the BBC Good Food caramel apple loaf cake or a banana bread decorated with caramel and dried banana chips. If you want to do something chocolatey, decorate it with maltesers as cling film goes easily over these without spoiling it!
If you'd rather do a round cake, surround the sides with Cadbury chocolate fingers and fill the top with maltesers. Google chocolate finger cakes for some inspiration... the end result can look stunning. You can then cling film tightly.
If you don't mind doing something other than the traditional cake, try a brownie tart or Bakewell tart, and there are some pretty solid cheesecake recipes where the biscuit base goes up the sides too.

And if you're going to transport inside a cake box, put in on a plate bigger than the cake, so the plate will knock against the sides and not the cake!