https://loco2.com/destinations/london-lisbon-train
London to Lisbon by train is an easy journey, one that can be accomplished in just under 24 hours. The obvious route is via Paris and then on over the Spanish border at Hendaye / Irun. There is just one departure daily. Leaving London at breakfast time and with a quick change in Paris, you’ll be at the Spanish border by early evening – just in time to connect at Irun onto the Sud Expresso (also sometimes called SUREX) night train which runs overnight to Lisbon.
If you are making this journey from Portugal towards Irun, note that the night train from Lisbon continues beyond Irun over the border bridge to terminate at Hendaye, the first station in France. A high-speed TGV service departs for Paris just over one hour after the overnight train from Lisbon pulls into Hendaye.
Tickets for the above journey from London to Lisbon become available three months in advance – and that’s when you get the best price.
One alternative favoured by many travellers is to break the journey in Spain. Travel from London to Barcelona and then continue at your leisure via Madrid to Lisbon. But bear in mind that the only direct trains from Madrid to Lisbon are overnight services. The Madrid to Lisbon hotel train is called the Lusitania. It departs from both the Spanish and Portuguese capitals just after nine in the evening.