In Wallis v Bristol Water plc, the Divisional Court has held that “likely to” implies a “real possibility” of an event occurring and does not mean “probable”.  

Bristol Water alleged that Wallis, a farmer, had committed an offence under Regulation 3(2) of the Water Supply (Water Fittings) Regulations 1999, as the taps installed in his dairy had been fi tted with inadequate backfl ow prevention. Regulation 3(2) states that it is an offence to install or use water fi ttings where it causes or “is likely to cause” contamination of water.  

Wallis was convicted but appealed on grounds of the meaning of “likely to”. Ignoring authority on the interpretation of this phrase, the court held that it was necessary to consider the context and aim of the specifi c legislation as a whole. It was held that the health risk involved and the potential for signifi cant harm if water contamination occurred made it “inherently unlikely” that the Regulations should be limited to cases where it was more probable than not that contamination would occur. The purpose of the Regulations is to protect people from water contamination; this supports the view of the court that “likely to” should be interpreted as a real possibility.  

There is widespread use of the phrase “likely to” in relation to environmental offences, so this decision may impact on many other areas of environmental law.