It's to let a contractor in for some emergency works that can't be done during the working day.
We have no staff contracted to work weekends and weekend overtime is not generally a thing, although obviously this would be paid or they could take time off in lieu if they prefer.
No one wants to do it. Who "should" do it? Do/can we "instruct" a junior member of staff or is this one of those occasions when senior staff need to step up?
What would happen where you work?