A Swearingen SA-227AC Metro III cargo plane, D-CAVA, sustained substantial damage in a landing accident at Dublin Airport (DUB), Ireland. Both crew members were not injured. Bin Air flight BID-3B originated in Manston International Airport, UK (MSE). The aircraft was cleared to land on runway 10 at Dublin. The approach was a CAT 1 approach. Weather conditions at Dublin were poor with visibility approximately 1,100 metres and a cloudbase of approximately 300 ft. Dublin was operating in low visibility abeyance. Runway Visual Ranges (RVRs) at 08:28 hrs were 1,600 m at touchdown, 1,800 m at midpoint and 1.600 m at stopend. The aircraft broke out of cloud at about 650 ft, approximately 200 ft above the minimum for the CAT 1 approach, and the pilots could see three white Precision Approach Path Indicator (PAPI) lights. As per normal procedure, after landing the First Officer who was Pilot Flying (PF) gave the controls to the captain who was Pilot Not Flying (PNF) so the he (PF) could complete the “Leaving the Runway” checklist. This checklist is completed from memory and included booster pump and flap-to-zero selections. The PNF recalled that during the landing roll, while the aircraft was braking and the indicated airspeed was below 90 kts, the nose gear suddenly collapsed. Both propellers contacted the runway surface and the aircraft quickly came to a halt resting on its nose. The Flight Crew then shutdown both engines, requested fire service assistance, selected batteries & generators to OFF and evacuated the aircraft through the cabin door. The Airport Fire Fighting personnel were on the scene within two minutes. There was no fire. The PF reported that it was a foggy day and that the approach was flown on limits with a lot of tension because of the uncertainty as to whether the aircraft would be able to land at Dublin. He described how concerns that fog might roll in raised his stress levels during the approach. During the landing roll, the landing gear selector was inadvertently moved to the UP position. This mistake was immediately recognised and the selector was returned to the DOWN position, but the nose-wheel retraction, which had been initiated, continued. The PF was unable to say definitively why the landing gear selector may have been mis-selected to UP, but he said that the intention may have been to move the Flap Selector instead. PROBABLE CAUSE: 1. Inadvertent selection of the landing gear selector to the UP position during the landing roll. CONTRIBUTORY CAUSES: 1. Reduced task focus by the PF following a tense and stressful limits approach. 2. Inactive landing gear interlock protection system due to the aircraft speed.