As I walked towards it there was a moment when the scale clicked into place and my jaw dropped: this yacht was HUGE. It's not so much a yacht as metallic cruise ship with the rig of a yacht.
The s/v Dwinger is a 46m long expedition aluminium sloop with an aero-rig and the tallest unsupported mast in the world at a height of 63m.
Everything about it was super-scaled, with the boom more like the crane on a construction site:
We agreed it was a whale of ship.
A bit of googling later on brought me to this news article with a video that is mostly in Icelandic apart from the interview with the skipper which is in English. It appears that this boat also was just back from Greenland.
Greenland was clearly the destination of choice for sailing yachts in Iceland. Which was fortunate as that was indeed where I was heading.