I have been with the company for 5 years and I was always doing day shifts or afternoon shifts finishing at 8pm the latest. Now after 5 years, my employer has put me on night shifts without my consent and I am refusing to do them and asking them to change rotas. I have a sleeping disorder and my husband has one too and went through multiple sleeping studies. He cannot fall asleep for hours if he gets woken up at night, and I would definitelly wake him up if I come home at night. Also, I don't drive a car so I would have to walk home at night on my own which I don't feel comfortable doing.
My employer is asking me to provide a written letter explaining why I cannot do night shifts. Is this legal, and what can I do in this situation? Any help would be appreciated.