Those don't look amazing but I wanted to post those for anyone who sees them. In London the policy is the train doesn't leave the station if there's graffiti on it. The train security is strong. These where photographed in the middle of a line so it's so hard to get these.
Yeah that tags marked .17 so last year. Also he was had an impact in Berlin in like 14/15 so yeah I think he's back around.
And to how they did it. I don't know. I've seen massive cut out stickers or even painting in the 20seconds the trains at the platform. Maybe a mistake by security? Maybe just outside a station there was a delay. Maybe they found a spot where the train stops for a few minutes, these things can be extremely well planned? I don't know these are guesses.