Luckily there are 2. Loss of one would not make a lot of difference. They can also be installed backwards!
Yes and no. The main job of these scissor links (as on any helicopter with MR swashplates) is to fix the rotating swashplate to the mast so that the whole assy turns as one. As RVDT is saying, if one link becomes detached for any reason, the other one will keep the swashplate fixed and rotating with the mast. The lower attachment nut on this link (the one I believe is the subject of this thread) even has a large cupped washer behind it to prevent the link completely detaching from the swashplate should the links lower bearing fail and come out of its outer race. Obviously, the washer and nut have to be fitted for this to happen.
This doesn't mean that single link detachment wouldn't be noticed in the cockpit.......in the Central Counties case, unusual vibration. Some helicopters only have one link, the EC135 has two. I would say that this was for a reason. Although the one remaining attached link would keep things together for a time..... factor in vibration, existing wear in the components and control input forces, and who knows what could happen??
For all you pilots who are now paying extra attention to the swashplate links on your Daily Inspections....the links are fitted the correct way round if the lettering is on the outward face of the link
The AAIB report will be an interesting one. If Wombats comments and the word on the street are 'on the button', then all the subsequent flight tests and the positioning flight from ECUK, as well as any operational flights at Central Counties were carried out with something 'amiss'.