Reposting here for traffic... I hope someone can help me out!
Did post in legal but no answer so far. I've searched ACAS and net but still can't find a definite answer.
Here's the situation, I've been called as a witness, the case is being heard in another county almost 200 miles from my home town. I was due to be working Mon to Thur off on Fri. My line manager has changed my shift to have me in on Fri, can she do this?
I don't know when I will be called by the court and if I do get home by Fri I can't guarantee I'd make the shift on time. I need to know if she can legal put me in for a shift none of us have a crystal ball confirming I'll be there for?
The other issue is after spending this week in court, which is really stressing me out, having me in on Fri means I'll be working 7 days straight on the back of a week at court with no day off in between. 
Thanks in advance