Oddness north of Wood Green today, and last week, on the Piccadilly Line.

There's this bit where all the lights are on in the tunnel, and all the main
lights go off in the carriage - so we're left with the lights streaming
through the windows from outside, and the ones above the doors still being
illuminated - so still bright enough, but imposible to read my newspaper.

Last week the train stopped and waited in Darkness Alley for a bit - this
week, it just sped through at normal speed.

What on earth is going on?

(Oh, and while answering that question, you might like to also fix the
signals near Arnos Grove while you're at it, because they're more stuffed
than a stuffed thing).