We had a beam not dissimilar to that, it was supported by absolutely fuck all. Make sure you see the ends of yours before you make any assumptions.
https://youtu.be/Y_KtQ1BqfHM
EDIT Not strictly true it's supported by at least 2 "structural" 4 X 2s and a sheet of plasterboard. That's pretty bad, and by pretty bad I mean appalling.
You forgot the closed door doing some heavy lifting too.
Is it a cowboy job to box in an acro prop ;)
@Bobbo started
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We had a beam not dissimilar to that, it was supported by absolutely fuck all. Make sure you see the ends of yours before you make any assumptions.