For a long time these two airlines were NCL's major customer; Air UK operating the AMS service, and the East Coast oil run with the F-27.  Dan Air operateed numerous scheduled services including LGW, but also had an extensive charter programme, which is probably what 'DE is doing in this pic.
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/130275500@N02">G B_NZ</a>
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/130275500@N02/23357942526/">Dan Air 737-200 G-BLDE at NCL</a>