Easiest train from London to Lyon

According to the Eurostar site, you can take the high-speed train from London St. Pancras to Lyon Part-Dieu without having to change.
https://www.eurostar.com/us-en/train/france/lyon

Eurostar as mentioned above, or fly with easyjet or Ryanair for a fraction of the price

The direct trains from London to Lyon only run certain days a week and leave very early in the morning. An alternative if you want to avoid changing stations in Paris is to look on the SNCF website or trainline.eu for journeys changing at Lille Europe rather than crossing Paris.

Which station in London do we depart from to go to Lille and onto Lyon. Are these the high speed trains? Thank you for your advice, we are first time train travelers out of London.

take the high-speed train from the station London St. Pancras to Lyon Part-Dieu
https://www.eurostar.com/us-en/train/france/lyon

All trains to France, both the ones all the way to Lyon and the one to Lille, leave from St Pancras.

If you don't want to have to get up before dawn in order to get the through Eurostar, all the information you need is here

We will be taking the 12:58 train from London St. Pancras arriving Lille Europe 15:30, transferring to the TGV train leaving Lille for Lyon at 15:54. The website suggests leaving at least 20 minutes for transfer within the station. Do we have to go through customs and is 24 minutes sufficient? Thank you for your advise!

https://help.eurostar.com/faq/be-en/question/What-security-checks-are-there-at-the-station

Note the section on check-in time, which says: "Check in at least 30 minutes before departure, 45 minutes at busy times like weekends and bank holidays." The security resembles an airport.

Seat 61 notes that immigration formalities for the "Continent" are performed at St-Pancras, station, inside the secure zone:
"There are no immigration formalities at the other end, it's all done before you board. So on arrival you just walk off the train, simple as that..."

I always caution riders on the Eurostar to arrive with Plenty of time. Sometimes there are no queues. Sometimes the queues are horrendous. Usually somewhere in between. 45-60 for me, at least.

The other connection will be straightforward, no customs, no passport control. All done at the origination station before you get on the Eurostar.

24 minutes will just about give you time for a coffee and a sandwich before the connecting train comes in.

24 minutes is fine for your connection time in Lille. As Southam and Nigel explained, you go through emigration FROM the UK and immigration INTO France BOTH in London at the Eurostar check-in. (It works the same way when leaving France -- both countries have their officials present, and you "leave" one country and "enter" into the other one, so when you actually arrive into the other country, you just walk scot-free off the train! Very nice.)

p.s. Business class is way more expensive on Eurostar than second class is (on some European trains, it doesn't cost much more, but this is one where it is expensive!). Look at the price differential before committing to traveling business class.

For the Eurostar train from London to Lille is Business Premier ( 1st class) worth the big difference in price?

For the Eurostar train from London to Lille is Business Premier ( 1st class) worth the big difference in price?

We usually go Standard Premier not Business Premier, and buy as far in advance as we are able for the max discount. With "Premier" you get food service and it is less crowded with a little more room.

Don't eat anything with meat on that train irrespective of class.

I personally think that second class is fine. It is about equal to business class on a plane. If it was a four or five hour, maybe an upgrade would be worth it but it is a very quick run. NIgel is absolutely correct. A couple of years ago it took over an hour to clear French immigration prior to boarding/

Very convenient from St Pancras to Lyon !!

Going St Pancras to Paris Nord, then Gare de Lyon to Lyon on the TGV is OK too but much better is St Pancras to Lyon, all the more so if you are pressed for time and encumbered by luggage.

Very true...get to St Pancras one hour ahead of your departure.

Standard class is effectively second class, but with large spaces between the seats, comfortable 2 + 2 seating. Going to Lille you will only be on the train a short time and unless somebody else is paying that's all you may need. Caffe Nero has a location in the St Pancras waiting room beyond check-in, security check and immigration x2 which does hot and cold drinks, and take away food suitable for the journey and time of day. There are also 2 food counter cars on the train.

Standard Premier is a small step up, with 1+2 seating, magazines, newspapers and a getting-worse-by-the-year-to-say-nothing-of-shrinking-to-virtually-nothing cold "meal" and coffee and tea service (in tiny cups) with some additional legroom for a moderate extra charge. Standard Premier still checks in at the same time as Standard.

Business Premier is the nose-bleed expensive more private area. The seats are identical to those in Standard Premier as is the legroom but with more personal service and perhaps a better meal (but at that price it should be on gold plates and served by wenches) and only a 10 minute check-in time, although how somebody, no matter how snooty, can check in, go through security and immigration x2 and get upstairs and onto the train in 10 minutes is beyond me.

I work on the British railway so get trips in Standard and Standard Premier fairly often. We aren't allowed anywhere near Business Premier.

A journey to Brussels or Paris is only 2 hours, Lille even less. When the trains were out of Waterloo several years ago and much slower Premier made sense to me as there was time to settle into the meal (which used to be hot and the real deal) and ambiance. There's not enough time now, IMHO.