The Nokia Lumia 630 expected to be one of the first handsets to arrive packing the Windows Phone 8.1 software has reportedly made an unscheduled appearance in a hands on video.
Unfortunately the video looks like it was shot by J.J. Abrams being chased by the Cloverfield monster, but it still gives us our clearest indication yet of what we can expect from Microsoft's forthcoming OS bump.
If you can avoid motion sickness, the clip below shows the improved Windows Phone UI, the new Action Centre notifications screen and the revamped camera interface.
The Lumia 630 is set to be a major upgrade over the Lumia 620, with a 4.5-inch 854 x 480 screen display, a quad-core Qualcomm Snapdragon 400 processor and 1GB RAM tipped in previous leaks.
Although the video below shows the a black prototype model, it is expected to launch in a range of bright colours.
The handset could also be joined by a new high-end model, with the Lumia 930 also rumoured to be arriving at Build, which kicks off in the first week of April.