backroom boys
US /ˈbæk.ruːm bɔɪz/
UK /ˈbæk.ruːm bɔɪz/

1.
people who do important work but have no contact with the public
:
•
The success of the campaign was largely due to the hard work of the backroom boys.
•
The scientists working on the secret project were the real backroom boys.