Norwegian Airlines has Denver to London Gatwick nonstop flights in April and May as low as $425 round trip. There are tickets at $180 one way on 6 dates between April 5 and May 3.
Even more surprising to me is seeing DEN-LGW one way at $196 on July 12 and $210 for 6 other dates in July.
While getting to London for $210 in July is a real deal, the price is substantially more to get back – starting at $570 one way LGW-DEN. This is where a miles award back to Denver can be a great value for a discount summer trip.
Norwegian Air Denver DEN – London LGW – Denver DEN