Opera install no workie (?)

I downloaded the file opera-stable_36.0.2130.65_amd64.deb to my freshly installed Ubuntu 16.04 system and then double clicked on it, which brough up the Ubuntu software installer. I then clicked on the Install button, and the install process seems to start, but then it just dies after a few seconds and opera does not in fact get installed.

What am I doing wrong? (This process seemed to work A-OK for the several other software packages I've already installed.)

Am I the only person this has happened to?

Is there something special that needs to be diddled in order to install opera from the .deb file?