The right of a worker to minimum rest periods contained in the Working Time Regulations 1998 can be modified for shift workers and in certain special cases (see Working Time Regulations 1998 reg 21. As well as emergencies the special cases include work involving security or surveillance or where round-the-clock staffing is essential as in hospitals, residential institutions, prisons, public utilities and industries where machinery must be kept working 24hrs in 24 - see notes at Working Time Regulations/Exemptions and exclusions .

The normal rules require a 20 minute rest break every 6 hours (see Working Time Regulations/rest breaks and weekends ). Where the special compensatory rest rules apply and the worker is required to work for more than six consecutive hours his employer "shall wherever possible allow him to take an equivalent period of compensatory rest" (save that in exceptional cases in which that is not possible, for objective reasons, the employer "shall afford him such protection as may be appropriate in order to safeguard the worker's health and safety" (Working Time Regulations 1998 (SI 1998/1833) reg 24).

BERR (formerly DTI) guidance notes point out that the intention and effect of the regulations is that even in these special cases workers will have the right to a minimum of 90 hours of rest in a week but that their rest can be taken in a different pattern to that set out in the basic regulations and state that "the principle is that everyone gets his or her entitlement of 90 hours rest a week on average, although some rest may come slightly later than normal" (see also notes in the program at Working Time Regulations/rest breaks and weekends ).

The BERR webpage on "More about application of the regulations" provides useful general guidance.

See also notes at Working Time Regulations/night work and/or Working Time Regulations/shift workers and/or Working Time Regulations/exemptions and exclusions .