Thames Water visiting

Yesterday I had two guys call in wanting to see waste pipes at back of house because they were conducting a pollution study. They showed me ID from Thames Water but since I hadn't had communication from Thames Water about such a study I was skeptical. My instinct said they seemed legit, they stayed 5 mines and were off.

Later I rang Thames Water to confirm they were in the area doing visits and after some time got a confirmation yes.

Moral of story, if uncertain about service people requesting access to your house, best to take photo of ID, ask persons to return at later date once you have had chance to verify they are legit.