If a worker is required to work for more than six hours at a stretch, he or she is entitled to a rest break of 20 minutes. The exact time the breaks are taken is up to the employer to decide.
(Workers under 18 are entitled to a 30 min break if working for more than 4.5 hours at a stretch)
Employers must make sure that workers
can take their rest, but are not required to make sure they
do take their rest.
Don't forget tho most of us aren't paid for our lunch break so if that applies to your brother he is fully entitled to not work for that entire hour.
http://www.legislation.hmso.gov.uk/si/si1998/19981833.htm#12