Fairly easy to extend it, though, as while one end has Luton directly next to it and a massive cliff (not as pronounced as it was with the road added I guess) the other end is just farmland. Offer the right price and it can easily be purchased for an extension.
(One could argue that extending it the other way over Luton would be an improvement, though)
It's not exactly flat at the western end either, would probably need some fairly significant earthworks to make a runway out of it.
This, and the airport have bought it anyway. But not for a runway extension.