Air India flight AI112 from LHR to Delhi reached the Dutch coast tonight (at FL310), did a descending loop north of Amsterdam, continued descent to FL150 at a fairly normal descent rate, continued up the north sea towards Denmark/Norway at FL150, then returned to LHR. Replay of the flight profile is available via this link;
Flightradar24.com - Live flight tracker!
I don't have any further information; just happened to notice the unusual flight profile on the flightradar24 web site.
Aircraft was a Boeing 777-337ER.