29. In any legal proceedings it will be presumed until the contrary is shown, that any sample—
(a)taken by virtue of the powers under this Schedule at a gauge, measuring station or other place provided in compliance with a condition imposed in an authorisation, is a sample, taken in accordance with those powers, of what was passing to the water environment at the place and the time recorded;
(b)taken in exercise of the powers under this Schedule in circumstances that an authorised person has agreed with the operator or responsible person the time when, and the points at which, samples are to be taken, is a sample taken under that agreement and in accordance with those powers, of what was passing to the water environment at the place and time recorded.