On Saturday afternoon I was messaged on Facebook that I was needed rather urgently at the observatory.
The guys had been sliding a new I beam into the floor void to reduce the bounce on the floor of the old section of the building and they had come across a problem. The fire alarm supply wire was in a really bad place and was going to cause major delays.
I went up there straight away, cut the wire, and removed the power from the panel.
Whilst I was there I snapped this photo under the floor of the new beam, now in position and ready to have the joists lowered back onto it.