From his other comments, perhaps the UK. In that case, the Wifi will vary greatly depending on the route — none on some lines, good wifi on others.

There's wifi on some Danish and Swedish trains, but now with free roaming I find it less reliable than my phone's data connection.

As the earlier reply speculated, I'm in the UK. I should add that sometimes I use my phone's mobile WiFi hotspot, which is equally good until we hit the standard middle-of-nowhere blackspot.