Thanks all for the quick responses. I can see the value in using additional resources to import as this looks to be a Darktable weakness, and pretty fundamental! I’ll try the suggestions and work rounds but may have to go down this route although I prefer to keep life simple. I’ll let you know how I get on. I should have said I’m using a Mac on which I am running Lightroom 5 with no difficulty - including on my brand new MacBook Air, having been told by Adobe that this was not possible.