Can my dp be forced to work weekends?

[aideesmum]

My dp has just been told that he HAS to work either next weekend (both sat and sun) or the following weekend. Then will be given time off in lieu in March.
He is on flexible working conditions and has to do his hours between 8am & 8pm Mon-sat (from memory, need to check contract tonight). He usually does Mon-Fri 8-5 ish.
Can they really make him work these weekends?

Check his contract. That is the starting point.

depends on his contract. it might say he has to have a certain amount of notice to a change in his hours. if it's just a one off what's the big deal?