What you suggested seemed to make lots of sense! So I tried to import the originals onto the iPad again directly from the SD card using the same lightning adapter but the iPad didn't recognise that the film clips were there - it didn't offer me the import button. I then recorded a few more seconds of film using the same camera onto that SD card and introduced it to the iPad in the same way. The iPad recognised that the new film clip was there because the import button appeared, but the only film it offered to import was my new test clip. All the time the MacBook Air has been happy to recognise and play all the original film clips. Between my very original import and this latest import attempt my friend used my SD card on his non-Mac laptop to download my clips. I can only think that this process has somehow changed the tagging of the clips. I appreciate you trying to help, thanks donwhine, but unless you have any more insight I think I have some hours of editing ahead of me! Not the end of the world!