While on a trip to Birmingham, we would like to take a quick side trip by train to London. What train station is London is best? We are mostly interested in seeing the regular tourist sites like Buckingham Palace, Westminster, and the Tower of London.
Thanks in advance.

It's not a case of "which is best", in most cases you won't have an option of which station.

In the case of trains from Birmingham most arrive at Euston (operated by Virgin Trains) but some arrive at Marylebone (operated by Chiltern Railways).

Note however that Chiltern uses Snow Hill & Moor Street in Birmingham whilst Virgin uses New Street - so you need to be certain which you are using.

Cheap tickets are never available before 12 weeks before the date of travel and may not appear until 6 weeks before in extreme cases. You can book at any of the following websites eastcoast.co.uk firstscotrail.com crosscountry.co.uk and collect at Birmingham

Thanks for the guidance. So, on arriving in London, do you think it is better to connect to a local train or to take a taxi to our final destination from the main arriving station?

If me I would take the Tube (subway).
check out the Tube Planner for details.

In your other thread, you said your companion will have surgery. Is this before or after your trip to London? How will it affect your companion's ability to climb stairs, walk in crowds, or other interactions you could expect in a crowded area? This could determine how you want to travel within London.

And if you're going back to Colorado, why would you opt for surgery in the UK?

"<i>So, on arriving in London, do you think it is better to connect to a local train or to take a taxi to our final destination</i>"

Impossible to say since you don't tell us what is the final destination.

The surgery is a mid-head hip replacement that is not yet approved by the FDA. She is an elite athlete, so the total hip replacement is a non-starter for her.
Dr. McMinn in Birmingham invented the procedure as well as hip resurfacing.
You raise a good point about her mobility. We are just going to have to feel that one out as we go. Her mobility has been remarkably good so far. She runs 100-mile races. She is pretty tough.

Typical FDA dithering.

Note that the Tube stations are largely not handicap-friendly and the Tube lines on the Underground (all but District, Circle, Metropolitan, and Hammersmith & City routes) are buried deep under the Earth (this is why the stations were bomb shelters in WWII) so if marathon woman is on crutches or in a wheelchair or similar, those cabs will look a lot better despite the cost.

You are right about the FDA. There are plenty of US surgeons that could do this procedure.
That is a good thought on the cabs.

Buses are a good option for seeing the city as you travel. You can purchase an all-day ticket when you get to the bus-stop. Try journeyplanner.tfl.gov.uk for routes to your intended places of interest.
Sometimes good bargain advanced rail tickets from Birmingham Moor St to London Marylebone. Check www.chilternrailways.co.uk
for promotions.

don't get confused with all the names in Birmingham and London - check the timetable on Nationalrail website and buy the tickets from them. Makes no difference which train company it is.
The best fastest is from Birmingham New Street - to London Euston - just over an hour.

http://www.nationalrail.co.uk/

"don't get confused with all the names in Birmingham and London "

But do realise that there are 3 stations in Birmingham from where you can travel to London and 2 in London where you can travel to Birmingham and turning up at the wrong station can be an expensive problem to fix.

Faster but more expensive to travel Birmingham New St to London Euston than Moor St to London Marylebone!

Sorry I take than back! Tomorrow's prices £41.90 return New St to Euston takes 1.24 hours
£47.90 from Moor St to Marylebone takes 2.22 hrs