That section starts with "This was the traditional approach...". I guess the Bakerloo and Picadilly line trains from the 1970s might still use them on London Un

That section starts with "This was the traditional approach...". I guess the Bakerloo and Picadilly line trains from the 1970s might still use them on London Underground? Wikipedia mentions stuff like GTO thyristers and IGBTs on descriptions of stuff like the 1992 (Central line) and 1995 (Northern) stock trains, so the next oldest trains from the 1990s seem to have modern(ish) power control. And new trains are coming to the Picadilly line, and presumably must come to the Bakerloo at some point before the old ones fall apart.