I found this by way of a tweet from the official account of the British Transport Police, which contained a link to a more detailed piece put out by Transport for London.
Unwanted sexual behaviour on public transport is not ok.#ReportItToStopIt
— BTP (@BTP) March 11, 2017
THE TFL “REPORT IT” PAGE
To visit the TFL “report it” page please click the image that concludes this post.