Thameslink Train Services Director Rob Mullen responded: "A very low level of legionella was found during testing in a small number of our Class 700 train toilets. While it is extremely unlikely this would cause any harm, the toilets were immediately locked out of use. The trains were taken out of service and these toilets have now been drained, bleached and had their tanks completely re-filled. There is no recorded case of anyone, ever, having contracted legionella from a train."