Alex from Tangancha wrote to me directly and gave me the link to the page with repo information. He also offered to do a specific Mint 10 link if this didn't work.
I'm pleased to say that the link that Alex gave me works fine and I now have 1.4.0 RC3 up-and-running. Very many thanks to Alex, (and others), for the replies - It's appreciated!! Ian Whitfield
