setup.bat (GitDependencies.exe) hangs when trying to prepare to build the source.

Hi - I’m trying to build UE from source - I’ve cloned the repo and run setup.bat and the first step (GitDependencies.exe) runs for a while and then hangs.

I’ve tried recloning the repo a few times and rerunning setup.bat and it always hangs at the same point:

Checking Dependencies…
Updating Dependencies: 93% (82259/103217), 19708.8/21094.8 MiB | 0.00 MiB/s…

Anybody know what is going on? A lot of googling hinted it could potentially be a firewall thing - if so, does anybody know what I should tell the IT guy to do with the firewall to allow this to go through?