For future ref, if lights are stuck on red and the beeping is really horrendous, it's worth considering whether putting them on their side is an option. Obviously you shouldn't do it if it will endanger people, but plenty of junctions will function fine without lights for a short period. You will feel quite odd putting lights on their side, but just look like it's your job and no one will question it! It's also a two person job.
I'd advise against putting them on their side, not easy, and not a good idea.
best to ring TfL, if within normal working hours, or they have an emergency contact out of hours call number, but if it's dangerous, then just ring the local police 101 number. They're surpisingly good and turn up a lot quicker than 'normal' police do.
I totally agree you shouldn't do it if dangerous but it's both TfL and the police who suggested to me to do it and when there is beeping all night (as we have had on Blackfriars Road), it really is impossible to carry on and ignore it. It would never have actually occurred to me if not suggested by someone, I'm not a traffic light anarchist!!!