Here's Sammie Welch, 23, with her 3-year-old son, Rylan.
Here's the note.
Have a drink on me.
You are a credit to your generation, polite & teaching the little boy good manners.
Man on train at table with glasses & hat.
Have a lovely evening.
P.S: I have a daughter your age. Someone did the same for her once! Hope when she has children she is as good a mother as you!
Welch posted about it on Facebook, and as you can imagine, it got shared pretty quickly.
The trip from Birmingham to Plymouth usually takes over three hours.
The stranger has been revealed. He's Ken Saunders, 50, from Wiltshire.