Last night I was awaken by roadworks around midnight to 1am near the Elephant and Castle. What on earth could they be digging up in the middle of the night? Fortunately, the works were not right in my street but I felt sorry for the poor people who had to put up with it.
If it is a red route I have been informed (on here, I believe) that they are allowed - obliged, no less! - to do the works at night in order to cause as little congestion as possible. So it does not even have to be anything important, always.