The invention relates to a leak detector (10) for detecting leaked liquid. The leak detector (10) comprises a flexible and elongate fastener (12) configured to fit around a liquid containing pipe to thereby attach the leak detector to the liquid containing pipe. The leak detector also comprises a leak sensor and a housing (14) containing electrical circuitry. The leak sensor (is) comprised in at least one of the fastener and the housing. The leak sensor is configured to sense liquid leaking from the liquid containing pipe with the electrical circuitry being operative to detect a leak in dependence on an output from the leak sensor. The leak detector is configured such that the housing (14) and the fastener (12) are abreast.