Luton-Copenhagen route has probably generated a whole new market that simply did not exist north of the Thames.
Did it not exist or was it just suppressed/locked? - discuss..
Two factors are normally in play on routes like this:
1. a "like for like" (fares not meaningfully cheaper) new route nornally stimulates a market to grow (lots of theories about why - mostly involving the surface access part of the "total trip cost" reducing the "travel decision threshold")
2. when prices suddenly nose dive to a destination loads of people rush to go because they have not been before - but then when everybody's been traffic stabilises at a new level.