london bridge what is this?

i see this EVERY day on my commute from the jubilee-northern line and vice versa and it’s been there for months, sometimes there will be a worker sitting on the chair. it doesn’t seem to have anyone “working” on it or anything. what is going on?

i see this EVERY day on my commute from the jubilee-northern line and vice versa and it’s been there for months, sometimes there will be a worker sitting on the chair. it doesn’t seem to have anyone “working” on it or anything. what is going on?