First time travelers to Paris/London in October

Since the tickets are bought, it is fairly academic now.

I wouldn't cut it so close if I were traveling.

Figure 2 hours from nominal arrival - when the wheels touch earth again - including taxi-ing, waiting to get off, walking the long walk, queueing for immigration, maybe a toilet break, and collecting luggage and getting out the frosted glass doors into the airport.

If you know exactly where you are going and the tube isn't playing up, an hour to St Pancras. A minimum 45 minutes to an hour for Eurostar check-in and security and 2 immigration queues.

So, 9:40 + 2 + 1 + 1 = 1:40pm.

I'd call it 10 minutes short, or you may just squeak it.

Pray for an early arrival, sit next to the exit door, research ahead your exact route, and cross your legs. You don't have time for that toilet stop.

You might take a taxi but at that time of day you will run into lunch time traffic.

You might Heathrow Express and tube or taxi but won't save much time and will have a longer wait if you just missed one.

Take the 15 minute Heathrow Express to Paddington Train Station and a 6 minute 3 mile taxi ride over to St. Pancras?

Oh my the sky is falling. Nigel has announced that you cannot do this and you’re going to be stuck all over 10 minutes. LOL

Since I did this in about two hours earlier this year. I know it can’t be done. The only real hangup, is going to be luggage. With the new scanning of your passport it’s not taking as long to get through immigration. But luggage at Heathrow can be slow if you’re doing carry on That makes it better

I took the Heathrow express. Yes I had to wait a few minutes for it but really it wasn’t bad. If you buy the tickets in advance it’s Not as expensive so I would go online at least 90 days in advance and buy them. I then took a cab to the train station. I will say that took longer than it should have because there was some event going on. But I still made it. My recommendation is don’t stop to shop ( no you don’t need anything) or eat until you get to the train station. Then if you have time there’s places to eat and shop. If worse comes to worse they sell food on the train, it’s not good but it’s food.

Assuming your plane is not several hours late you won’t have any problem.

If it were me I would get out of the airport as quickly as possible and catch a taxi direct to St.Pancras. I have found the least amount of changes in transportation the better when you are in a time crunch. Every change in modes of transport can be a potential delay, especially if you are unfamiliar with the metro and you look for your stops, buy tickets, wait in line to use a machine or service window, etc. There may be traffic, but that is a risk you have to take. If you miss your Eurostar, there will be another in about 30-60 minutes. It's only a few bucks, don't let it stress your vacation from the start.

Paddington to Kings Cross is a busy route daytime. I take the Bus#205 from Paddington after getting off the Express and it takes another ca 35 mins to reach Kings Cross.