All reports indicate the Ben My Chree was indeed in Birkenhead being repaired on the 17th June 1940 BUT, at least 4 independent accounts have her at St Nazaire on the 17th, the day the Lancastria was hit. The IOMPSC was of no help. I have the movement card and log but there are gaps. There is also the fact the Navy took over the ship in early June (and pranged it).
The following is a message from WW2Talk forum
Hello,
I've just seen your post about the Ben-my-Chree and St Nazaire. My great-grandfather was also shipped out on the Ben-my-Chree from St Nazaire, he told my grandfather that the ship in front of them sank (the Lancastria). Everyone has been telling me, and you, that that the Ben-my-Chree didn't evacuate anyone from there but it strikes me as strange that both my great-grandfather and your relative should remember something so utterly wrong. It's not even like a ship with a similar name shipped out from there. I just wanted to say hello and add my support to the belief that the Ben-my-Chree evacuated troops from St Nazaire!
Kind regards,
Elissa
The mystery deepens even more