Advice regarding honoured holidays.

My partner booked a week off in his old job last year,( the week being last week.) Since then he has started a new job. He was promised to have his holidays honoured and paid, however he was approached today and told he wont be paid for the holiday, and will need to cancel any future time off to essentially break even and not owe the company time. I know its not a legal requirement for a company to honour holidays, but isnt that before you take it? I want to ask what to do regarding a company going back on their word and changing their mind after the holiday has passed.