"The mattress is halfway

off the base again," the Senior Cat tells me, "Can you help me push it back?"
It is not the first time this has happened - and it will not be the last. 
The Senior Cat is an incredibly restless sleeper. He tosses and turns and flings his arms and legs in all directions. He has always done this. 
As a child his mother used to pin the blankets to the mattress in order to keep him covered - after he outgrew her homemade sleeping bags. In adolescence he would wake in the middle of the night feeling cold - because the blankets were on the floor. When he shared a bedroom with a fellow teacher in one of his country appointments before his marriage he nearly drove his fellow boarder mad - somehow they are friends to this day but it is remarkable.
When he married my mother the marriage survived because they spent (most of) the nights in separate beds. My mother would have been a battered and bruised woman because he is so restless. 
The Senior Cat has been known to find himself on the floor -fortunately no damage has ever been done but I wonder at it.  I do not know anyone as restless as he is.
I am not a tidy sleeper myself. I know I am rather restless but I am not as bad as he is. It is as if he has endeavoured to climb Everest during the night.
Fitted bottom sheets have helped a little, at least the bottom sheet is now more inclined to stay on the bed. These days I sneakily turn one of the blankets sideways. There is more to tuck in on each side that way. The blanket stays on a little longer that way. (Yes, forget an eiderdown, quilt or duna. It would not stay put.)
And today is the day I change his sheets. Today I also have a very early appointment at the hospital. I have left strict instructions for the Senior Cat.
I have said, "Please do not try and make your bed with the fresh sheets. I will do that. That way I will know that, perhaps, for one night the bed may stay together long enough for you to get a good night's sleep."
I rather doubt he is ever going to learn to tuck the bedclothes in properly - and then stay there. Perhaps it is impatience to get on with life?