Buildersmate is correct regarding the law. As regards your particular situation, if your manager has such a problem with this, one would have thought they would have a clause in your contract specifying the periods in which you take your breaks. For example, I work a 12-hour shift and get 2 paid 30-minutes breaks. My contract stipulates that I take the first break in the first half of the shift, the second break in the second half and that neither is taken in the first 2 hours nor the last 2 hours of the shift. So, if I wanted to, I could take my first break after 5-and-a-half hours and the second after 6 hours. That is, take my full entitlement together as 1 hour. There is nothing in the law that specifies when you must take your breaks, only what breaks you are entitled to. It is a matter for you and your manager to agree upon.