Best museum in London for trains for 5 year old?

[Terramirabilis]

No response elsewhere so trying again here:

We'll be in London for two days later this year from overseas and have a train-mad soon to be 5 yo DS. We can make it to only one museum/location for trains for him during our stay.

Anyone know which is likely to suit him best? Possibilities I'm weighing are Kewbridge Steam Museum, the London Transport Museum and the Science Museum. But perhaps there are others I don't know about.

We will also be using the tube so he will get a bit of a fix from that.

I've lived in London in the past so no worries about getting around, navigating buses etc. I just haven't spent much time in train museums previously!

The Transport Museum. The Steam Museum only has a steam train running on weekends. It is a steam museum rather than a train museum. The science museum doesn’t have much train related. The Transport Museum is your best bet.

The Transport Museum would be easier since it's very central so it's good to hear that it's the best option.

Get there early if you can as it does get busy on the weekends. Know that it's relatively small.

P.s. Check out their open weekends in their depot in Acton just in case you're in town on the right dates.

Took my daughters to the Transport Museum many years ago when they were doing transport at school. I expected it to be fairly dull but we all loved it. Really worth a visit and kids get in free too! Lots of street artists to see around Covent Garden too which will add to the experience.

Really cool play zones at the Transport Museum if you are into trains. Eg child size tube carriage/uniforms etc. All good fun!

The Postal Museum has a mail train underground that you can ride on.

My kids loved the Transport Museum when they were little. Don't even live near London but we went several times!
They moved on to the Science Museum later on.

@SleepDeprivedCabbageBrain I saw the depot thanks but unfortunately we're not there when it's an open day.

@flissfloss65 How long is the ride, do you know? I'm guessing most of the museum is postal rather than trains based on the name.

Transport museum- he will love it. It's a no brainer.

Also the DLR is a good shout. Sit at the front and pretend you are the driver!