Travelling to Turin is easier and more pleasant than one might think. It is possible to travel to Turin and beyond in a day from London, or travel to Paris in the evening and take a sleeper, or spend the night in Paris and travel over the next day.
If you leave in the evening to spend the night in Paris, you can be in Turin for lunch. See the Man on Seat 61 fpr some options.
Of course, affluent Eagles could always take the Orient Express.