Arrival at Heathrow - Time Needed to Get to Tube?

Obviously no one can tell you with certainty how long it will take you.

Here is an “average” time for me. 20-30 minutes to deplane and walk to passport control. 10 minutes through Passport control. 30 minutes if waiting for a checked bag. 20 minutes walk to the tube.

It could go faster or slower. Have you thought about eliminating the stress of this by simply staying at. An airport hotel that night?

Unless something goes horrendously wrong with your arrival you will have plenty of time to catch the tube. At that time of night it will be perfectly possible to be on the tube by 22.30. The last train into the city leaves at 23.22 on Sunday, 23.45 Monday to Thursday and it runs all night on Friday and Saturday.

There is also a 2352 Elizabeth Line (change at Paddington for central London) and a 0012 Elizabeth Line train to Paddington.
Every night of the week there are National Express coaches to Victoria Coach Station at 2359, 0100 and then frequent from 0345, and a night bus, N9, every 30 minutes, every night of the week to Trafalgar Square, which takes 1 hour 10 minutes.
So you would never get stuck at Heathrow, no matter how late your flight arrived.

Delta arrives at Terminal 3. Brussels arrives at Terminal 2.

Unless your flights are really delayed, or there is some problem with Immigration, you shouldn't have a problem. If you have an American passport, you can use the egates and not have to speak to anyone. If there is a problem with machines reading your passport, you will be sent to a side desk for verification but this is not the regular passport line and shouldn't take too long.

The last time I arrived at T3, it was about the same time at night as your Brussels flights and I was checked into my hotel near T2 within one hour of touchdown.

You have loads of time, there will be numerous flights after yours and Underground running for at least two hours any day of the week, longer on others

Thank-you all. I have a hotel booked for the night near an Elizabeth Line stop. On the Heathrow Airport website I was able to type in my estimated departure time from the airport and the address of my hotel and get an exact route with timing given. So I should definitely be at my hotel before 11:30 PM at the latest - or 23:30 in 24 hour time. If going through customs is super fast I could even be there earlier than that.

To Frank II - what are egates? Do I need Global Entry or Clear in addition to my U.S. passport to use egates?

GE and Clear are only when you return to the Big PX, my travel partner was grumbling that they weren't any good for leaving the UK. Or entering either.

Egates are electronic gates that allow you to bypass speaking with an agent. You put your passport in the slot, look at the camera, and if you look like the photo in your passport, the gate opens and off you go.

As a U.S. passport holder, follow the signs (US Flag) and you will automatically be directed to the egates.

Frank II is correct, it's all automated. Perhaps a bit too much, but as they say on their signs, we are simply keeping track of everyone entering and exiting the country they don't need or want to talk to almost any of them.

Thanks Frank II and phred for the additional information about egates and signs.