bang on about (something)

To speak continuously or at great length about something in a foolish, tedious, or irritating manner. Primarily heard in UK. Tom is always banging on about his plans of becoming some great author, but he never writes a blooming thing! What on earth are you banging on about? You really have no idea how politics works, do you? He used to be a college professor, so he can bang on about any topic for hours on end.