reg 18
(1) A project licence must include a condition requiring the holder to ensure that the regulated procedures applied as part of the specified programme of work are those which to the greatest extent meet the following requirements— (a) use the minimum number of animals; (b) involve animals with the lowest capacity to experience pain, suffering, distress or lasting harm; (c) cause the least pain, suffering, distress or lasting harm; (d) are most likely to provide satisfactory results. (2) A project licence must include a condition requiring the holder to ensure that the regulated procedures applied as part of the specified programme of work are designed so as— (a) to result in the death of as few protected animals as possible; and (b) to reduce to the minimum possible the duration and intensity of suffering caused to those animals that die and, as far as possible, ensure a painless death.