Can't Clone Git Respository in SourceTree: Failed to connect....No error

While attempting to clone a Git based repository in Stash via the SourceTree client, I received the following error:

fatal: unable to access ‘http://[email protected]:443/repo.git/': Failed connect to company.local:443; No error

No error obviously doesn’t give many clues, however this post suggested something to do with proxy settings.

My web browsers were configured to use an internal web proxy via an automatic configuration script and I could successfully navigate to the repository via a web browser. My SourceTree client appeared to be configured correctly since it was set to use the same proxy settings:

The aforementioned post suggested that it was actually the Git command line tools which also need to be configured to use a proxy and the handy checkbox Add proxy server configuration to Git / Mercurial does that for you.

I configured that setting and lo and behold could then clone the repository.