Up to 400,000 public sector employees, including police officers, lecturers and border control staff, are staging a day of protest against the government austerity program, with thousands of people expected to attend events in central London.

Important to note is that police officers cannot strike. The last time they did so was in 1918 and 1919. The government feared anarchy and very quickly banned officers from striking ever again. So the officers who march have taken the day off work and they won't be in uniform.