You can now travel all the way from Portugal to Singapore by train: https://www.msn.com/en-gb/lifestyle/travel/you-can-now-travel-all-the-way-from-portugal-to-singapore-by-train/ar-AARNt8b?ocid=msedgntp
I don't think I could sit for 20 odd days on the trot on a train unless it was the Orient Express with all the old fashioned trimmings and a host of modern ones... An extremely staggered journey to be able to see the sights along the way could be considered, provided Camelot gets friendlier.
