The North Sea fields, which lie in the ocean sort of midway between England and Norway, were discovered in the 1970's, which is somewhat late in the oil discovery game.
As a result of a number of factors (being found late in the oil discovery game; being located between two countries interested in their development; having been developed by Western oil companies; because they were used to offset the power of OPEC) these fields were developed with some of the most advanced technologies available.
What was the result? They produced a lot, and they produced very quickly.
This is the unfortunate end result.
[Here's something I've been wondering: Does the application of advanced technology affect Hubbert's Peak? I mean, with most of the big fields being on the older side, and having brought in advanced technologies say, 1/3 or 1/2 way into their lifespans, does it possibly change the shape from a bell curve to something different? Maybe say, the shape of a children's slide. Only with the steps leading up (the steeper incline) on the right side (after the peak). I think they have made some adjustments for this in the current models though. I'll have to read up further.]